Losartan Potassium (losartan potassium)

Available as losartan potassium; dosage is expressed in terms of the salt.

Losartan potassium is administered orally without regard to meals. It is available as oral tablets. It is also commercially available in fixed-combination tablets containing losartan potassium and hydrochlorothiazide; see the full prescribing information for administration of this combination product.

Losartan potassium tablets should be stored at 25degreesC (excursions permitted between 15-30degreesC) and protected from light.

For pediatric patients or patients unable to swallow tablets, losartan may be administered orally as an extemporaneously prepared suspension. An extemporaneous suspension containing losartan potassium 2.5 mg/mL can be prepared in the following manner. First, add 10 mL of purified water to a 240 mL amber polyethylene terephthalate (PET) bottle containing ten 50-mg tablets of losartan potassium. Shake the contents for at least 2 minutes. Allow the concentrated suspension to stand for 1 hour and then shake for 1 minute to disperse the contents. Separately, prepare a mixture containing equal parts (by volume) of syrup (Ora-Sweet SF(R)) and suspending vehicle (Ora-Plus(R)). To the concentrated suspension of losartan, add 190 mL of the Ora-Sweet SF(R) and Ora-Plus(R)mixture, and shake for 1 minute to disperse the ingredients. Refrigerate the suspension at 2-8degreesC. Shake the suspension before dispensing each dose and return promptly to refrigeration. The extemporaneous suspension is stable for up to 4 weeks when stored at 2-8degreesC.

In vitro studies indicate that cytochrome P-450 (CYP) 2C9 and 3A4 are involved in the biotransformation of losartan to active and inactive metabolites.

Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

Ace Inhibitors; Arbs; Eras; Aliskiren/Sparsentan

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Sparsentan is an antagonist of the endothelin type A receptor and the angiotensin II type 1 receptor which are thought to contribute to the pathogenesis of IgA nephropathy.(1) Coadministration with renin-angiotensin-aldosterone system (RAAS) inhibitors and endothelin receptor antagonists (ERAs) may result in additive inhibition of angiotensin. RAAS inhibitors include ACE inhibitors, angiotensin II receptor blockers (ARBs), and aliskiren.

CLINICAL EFFECTS: Concurrent use of sparsentan with renin-angiotensin-aldosterone system (RAAS) inhibitors and endothelin receptor antagonists (ERAs) may result in hypotension, syncope, hyperkalemia, and changes in renal function (including renal failure).(1)

PREDISPOSING FACTORS: Patients with renal artery stenosis, chronic kidney disease, severe congestive heart failure, or volume depletion may be at risk of developing acute kidney injury on sparsentan.(1) Patients with advanced kidney disease or taking concomitant potassium-increasing drugs (e.g., potassium supplements, potassium-sparing diuretics), or using potassium-containing salt substitutes are at increased risk for developing hyperkalemia.(1)

PATIENT MANAGEMENT: Do not coadminister sparsentan with renin-angiotensin-aldosterone system (RAAS) inhibitors and endothelin receptor antagonists (ERAs). Prior to initiating treatment with sparsentan, discontinue use of renin-angiotensin-aldosterone system (RAAS) inhibitors and endothelin receptor antagonists (ERAs).(1) RAAS inhibitors include ACE inhibitors, angiotensin II receptor blockers (ARBs), and aliskiren.

DISCUSSION: The US manufacturer of sparsentan states that concomitant use of sparsentan with renin-angiotensin-aldosterone system (RAAS) inhibitors and endothelin receptor antagonists (ERAs) is contraindicated.(1) RAAS inhibitors include ACE inhibitors, angiotensin II receptor blockers (ARBs), and aliskiren.

Selected Nephrotoxic Agents/Bacitracin

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Bacitracin may cause renal failure due to glomerular and tubular necrosis. Concurrent administration of other nephrotoxic agents may result in additive renal toxicity.(1-3)

CLINICAL EFFECTS: Concurrent use of bacitracin with other potentially nephrotoxic agents may result in renal toxicity.(1-3)

PREDISPOSING FACTORS: Dehydration and high-dose bacitracin may predispose to adverse renal effects.(1)

PATIENT MANAGEMENT: Health Canada states that bacitracin is contraindicated in patients with renal impairment, including those taking other nephrotoxic drugs.(1) The Canadian and US manufacturers of bacitracin state that concomitant use of bacitracin with other potentially nephrotoxic agents should be avoided.(2,3)

DISCUSSION: Renal impairment is a major toxicity of bacitracin. Cases of nephrotoxicity have been reported when bacitracin was used off-label.(1-3)

Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

Ace Inhibitors; Arbs/Aliskiren

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: The exact mechanism is unknown.

CLINICAL EFFECTS: In the ALTITUDE study, concurrent use of aliskiren for 18-24 months in patients maintained on either an ACE inhibitor or an ARB resulted in an increase in non-fatal stroke, renal complications, hyperkalemia, and hypotension.(1,2)

PREDISPOSING FACTORS: Patients with Type II diabetes and/or renal impairment may be at a higher risk from this combination.(1)

PATIENT MANAGEMENT: Novartis no longer recommends the concurrent use of aliskiren with either an ACE inhibitor or an ARB.(1,3) Hypertension regimens of patients receiving concurrent therapy should be re-evaluated.(1) Concurrent use of aliskiren in diabetic patients receiving either an ACE inhibitor or an ARB is contraindicated.(2,4) Avoid the combination in patients with CrCl less than 60 ml/min.(5)

DISCUSSION: ALTITUDE was a multinational study designed to evaluate the use of aliskiren for more than 1 year in patients with Type II diabetes and renal impairment, who are known to have a high risk for cardiovascular and renal events. Aliskiren was given with optimal cardiovascular treatment, including an ACE inhibitor or ARB. After 18-24 months of concurrent therapy with aliskiren and either an ACE inhibitor or an ARB, there was an increase in non-fatal stroke, renal complications, hyperkalemia, and hypotension.(1,2)

Ace Inhibitors; Arbs/Lithium

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Angiotensin converting enzyme inhibitors (ACEI) or angiotensin II receptor blocker (ARB)-induced sodium loss or volume depletion may result in decreased renal clearance of lithium.(1)

CLINICAL EFFECTS: Concurrent use of ACEI or ARBs may result in elevated lithium levels and lithium toxicity. Lithium has a narrow therapeutic range. Unintended increases in lithium concentrations may lead to lithium toxicity. Early symptoms of lithium toxicity may include: lethargy, muscle weakness or stiffness, new onset or coarsening of hand tremor, vomiting, diarrhea, confusion, ataxia, blurred vision, bradycardia, tinnitus, or nystagmus. Severe toxicity may produce multiple organ dysfunction (e.g. seizures, coma, renal failure, cardiac arrhythmias, cardiovascular collapse) and may be fatal.(1)

PREDISPOSING FACTORS: Risk factors for lithium toxicity include: acute renal impairment, chronic renal disease, dehydration, low sodium diet, and concomitant use of multiple medications which may impair renal elimination of lithium (e.g. ACEI, ARBs, NSAIDs, diuretics).(1) Patients who require higher therapeutic lithium levels to maintain symptom control are particularly susceptible to these factors.

PATIENT MANAGEMENT: If concurrent therapy cannot be avoided, monitor closely. Evaluate renal function and most recent lithium levels. If renal function is not stable, whenever possible delay initiation of concurrent therapy until renal function is stable. The onset of lithium toxicity due to concomitant therapy with an ACEI or ARB may be delayed for 3-5 weeks.(2) Patients receiving this combination should be observed for signs of lithium toxicity when the ACEI or ARB dose is increased or if additional risk factors for lithium toxicity emerge. If an ACEI or ARB is required in a patient stabilized on lithium therapy, check baseline lithium concentration, consider empirically lowering the lithium dose, then recheck lithium levels 5 to 7 days after ACEI or ARB initiation. Adjust lithium, ACEI or ARB dose as required and continue frequent (e.g. weekly) monitoring of lithium until levels have stabilized. If lithium is to be started in a patient stabilized on an ACEI or ARB, consider starting with a lower lithium dose and titrate slowly as half-life may be prolonged.(1) Monitor lithium concentrations frequently until stabilized on the combination. If an interacting drug is discontinued, the lithium level may fall. Monitor lithium concentration and adjust dose if needed.(1) Counsel patient to assure they know signs and symptoms of lithium toxicity and understand the importance of follow-up laboratory testing.

DISCUSSION: Elevated lithium levels and lithium toxicity have been reported during concomitant administration of lithium and an ACEI(3-17) or an ARB(18-20). Other factors, such as dehydration, acute or worsening of chronic renal impairment, or acute changes in sodium intake may increase the occurrence of a clinically important interaction.

Ace Inhibitors; Arbs/Sodium Phosphate Bowel Cleanser

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Bowel cleansing with sodium phosphate causes dehydration, decreased intravascular volume and hyperphosphatemia, which increases phosphate levels in the renal tubules. Abnormally high levels of calcium and phosphate in the renal tubules may precipitate out, resulting in renal injury.(1)

CLINICAL EFFECTS: Use of sodium phosphate for bowel cleansing in patients maintained on angiotensin converting enzyme (ACE) inhibitors, angiotension receptor blockers (ARBs) may increase the risk of acute phosphate nephropathy, which is an acute kidney injury associated with deposits of calcium phosphate crystal in the renal tubules that may result in permanent renal function impairment. Acute phosphate nephropathy presents as acute kidney injury with minimal proteinuria and a bland urine sediment.(2) Use of sodium phosphate products at laxative doses has not been associated with acute kidney injury.(3)

PREDISPOSING FACTORS: Patients who may be at an increased risk of acute phosphate nephropathy include those who are over age 55; are hypovolemic or have decreased intravascular volume; have baseline kidney disease, bowel obstruction, or active colitis; and who are using medications that affect renal perfusion or function (such as diuretics, ACE inhibitors, ARBs, and possibly nonsteroidal anti-inflammatory drugs (NSAIDs).(2)

PATIENT MANAGEMENT: If possible, use an alternative agent for bowel cleansing.(1) Use sodium phosphate products with caution in patients taking medications that affect kidney function or perfusion, such as ACE inhibitors or ARBs. Obtain baseline and post-procedure labs (electrolytes, calcium, phosphate, BUN, creatinine, and [in smaller, frail individuals] glomerular filtration rate). Instruct patients to drink sufficient quantities of clear fluids before, during, and after bowel cleansing and to avoid other laxatives that contain sodium phosphate. Consider hospitalization and intravenous hydration during bowel cleansing to support frail patients who may be unable to drink an appropriate volume of fluid or who may be without assistance at home.(2) Use of an electrolyte solution for rehydration may decrease the risk of acute phosphate nephropathy.(4,5)

DISCUSSION: Since May 2006, the FDA has received 20 reports of acute phosphate nephropathy associated with the use of Osmo Prep. Concomitant medications included ACE inhibitors or ARBs (11), diuretics (6), and NSAIDs (4).(2) In a retrospective review of colonoscopy patients, simultaneous use of ACE inhibitors or ARBs significantly increased the risk of acute kidney injury from oral sodium phosphate. Diuretic use was also a risk factor.(6) In a case series study of 21 cases of acute phosphate nephropathy in patients who had used oral sodium phosphate, 14 patients received an ACE inhibitor or ARB, 4 used a diuretic, and 3 used an NSAID.(7) Cases have also been reported with rectal products.(8)

Ace Inhibitors; Arbs/Trimethoprim

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: ACE Inhibitors, Angiotensin Receptor Blockers (ARBs), and trimethoprim have all been proven to increase serum potassium levels. The increase is achieved by reduction in potassium elimination by trimethoprim(1,2) and a decrease in angiotensin activity by ACE Inhibitors and ARBs. The use of these medications in combination can have an additive effect on serum potassium resulting in potentially dangerous levels.(1-5)

CLINICAL EFFECTS: Concurrent use of trimethoprim and ACE Inhibitors or Angiotensin Receptor Blockers may result in increased serum potassium levels,(1-5) which may be fatal.(2)

PREDISPOSING FACTORS: The interaction may be more significant in elderly patients and patients with renal insufficiency.(1)

PATIENT MANAGEMENT: Use trimethoprim with caution in patients maintained on ACE Inhibitors or ARBs. Patients using these medications concurrently should have their serum potassium monitored. In the elderly or renally impaired, alternative antibiotic therapy should be considered.

DISCUSSION: In a retrospective review of patients in Ontario maintained on an ACE inhibitor or ARB who were admitted to a hospital for hyperkalemia within 14 days of receiving a prescription for SMX-TMP, amoxicillin, ciprofloxacin, norfloxacin, or nitrofurantion, 371 patients were identified. More than half of the patients with hyperkalemia had received SMX-TMP. Patients receiving SMX-TMP had a 7-fold increased risk of hyperkalemia compared to patients receiving other antibiotics. No risk was found with the other antibiotics.(1) A retrospective review of patients in Ontario maintained on an ACE inhibitor or ARB examined those who died within 7 days of filling an outpatient prescription for amoxicillin, ciprofloxacin, norfloxacin, nitrofurantoin, or SMX-TMP. Patients receiving SMX-TMP had an increased risk of death (adjusted odds ratio 1.38) compared to amoxicillin. Risk was slightly higher at 14 days (adjusted odds ration 1.54). This corresponded to 3 sudden deaths within 14 days per 1000 SMX-TMP prescriptions.(2) A review of nine case reports of hyperkalemia with SMX-TMP found that 2 patients were receiving concurrent ACE inhibitors (enalapril and benazepril). One of these patients had severe hyperkalemia with a peak potassium level of 7.4 mEq/l.(3) Hyperkalemia has also been reported with concurrent SMX-TMP and enalapril(4) and with quinapril.(5)

Selected Nephrotoxic Agents/Colistimethate

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Colistimethate can cause nephrotoxicity.(1,2) Concurrent administration of other nephrotoxic agents may result in an increased risk of nephrotoxicity.(1) It is suspected that cephalothin interferes with the excretion of colistimethate resulting in enhanced nephrotoxicity.(2,3)

CLINICAL EFFECTS: Concurrent use of colistimethate with other nephrotoxic agents may result in additive nephrotoxic effects.

PREDISPOSING FACTORS: Factors predisposing to nephrotoxicity include higher cumulative doses of colistimethate, longer treatment duration, hypovolemia, and critical illness.

PATIENT MANAGEMENT: Concurrent use of potentially nephrotoxic agents with colistimethate should be avoided.(1,2) If concurrent use is necessary, it should be undertaken with great caution.(1)

DISCUSSION: In a case control study of 42 patients on intravenous colistimethate sodium, NSAIDs were identified as an independent risk factor for nephrotoxicity (OR 40.105, p=0.044).(4) In 4 case reports, patients developed elevated serum creatinine and blood urea nitrogen following concurrent colistimethate and cephalothin (3 patients) or when colistimethate followed cephalothin therapy (1 patient).(3) A literature review found that individual nephrotoxic agents, including aminoglycosides, vancomycin, amphotericin, IV contrast, diuretics, ACE inhibitors, ARBs, NSAIDs, and calcineurin inhibitors, were not consistently associated with additive nephrotoxicity when used with colistimethate. However, when multiple agents (at least 2 additional potential nephrotoxins) were used concurrently, there was a significant correlation to colistimethate nephrotoxicity.(5)

Moderate Interaction: Assess the risk to the patient and take action as needed.

Ace Inhibitors; Arbs/Drospirenone

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Drospirenone has antimineralocorticoid activity and may cause hyperkalemia. ACE inhibitors and angiotensin II receptor antagonists may also increase potassium levels.(1)

CLINICAL EFFECTS: Concurrent use of drospirenone and ACE inhibitors or angiotensin II receptor antagonists may result in hyperkalemia.(1)

PREDISPOSING FACTORS: Renal insufficiency, hepatic dysfunction, adrenal insufficiency, and use of potassium supplements, potassium-sparing diuretics, heparin, and NSAIDs may increase potassium levels.(1)

PATIENT MANAGEMENT: Patients receiving drospirenone with either an ACE inhibitor or an angiotensin II receptor antagonist should have their serum potassium level checked during the first treatment cycle.(1)

DISCUSSION: Drospirenone has antimineralocorticoid activity comparable to 25 mg of spironolactone and may result in hyperkalemia. Concurrent use of ACE inhibitors or angiotensin II receptor antagonists may also increase potassium levels.(1) In a study in 24 mildly hypertensive postmenopausal women who received concurrent drospirenone/estradiol (3 mg/1 mg) with enalapril (10 mg), mean serum potassium levels were 0.22 mEq/L higher than in the placebo group. On day 14 of concurrent therapy, the ratios for serum potassium maximum concentration (Cmax) and area-under-curve (AUC) were 0.955 and 1.010, respectively. No patient developed hyperkalemia.(1)

Ace Inhibitors; Arbs/Loop Diuretics

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: The exact mechanism is unknown. The initial hypotensive effect of the ACE inhibitors is mainly the result of suppression of the renin-angiotensin-aldosterone system. The ACE inhibitors inhibit the formation of angiotensin II and angiotensin II receptor antagonists block the action of angiotensin II, thereby lowering aldosterone levels with subsequent sodium and water depletion. Agents such as the loop diuretics that cause sodium and water loss may exaggerate the hypotensive state.

CLINICAL EFFECTS: The addition of an ACE inhibitor to a patient receiving a loop diuretic may result in severe postural hypotension. This effect is transient and is not expected to occur during long-term dosing. Symptomatic hypotension may result in patients treated with loop diuretics who are started on an angiotensin II receptor antagonist. Concurrent use of a renin-angiotensin system (RAS) inhibitor with diuretics and NSAIDs may result in increased risk of acute kidney injury (AKI).

PREDISPOSING FACTORS: Addition of an ACE inhibitor or an angiotensin II receptor antagonist to a patient already receiving a diuretic or who is sodium depleted. Low water intake/dehydration, drug sensitivity, greater than 75 years of age, and renal impairment may increase an individual's susceptibility to AKI.

PATIENT MANAGEMENT: In patients without heart failure, it may be advisable to discontinue the diuretic, reduce the dose of the diuretic, or increase salt intake prior to the initiation of the ACE inhibitor. If hypotension occurs, place the patient in a supine position. Hypotension is most likely when the ACE inhibitor is initiated. However, if subsequent hypotension occurs, a dosage adjustment or discontinuation of one agent may be required. Intravascular volume depletion should be corrected in patients prior to the initiation of an angiotensin II receptor antagonist. Concurrent use of a RAS inhibitor with loop diuretics and NSAIDs should be used with caution and monitored closely for signs of AKI.

DISCUSSION: In a computational study, the risk of AKI using triple therapy with a diuretic, renin-angiotensin system (RAS) inhibitor, and NSAID was assessed. The study found the following factors may increase an individual's susceptibility to AKI: low water intake, drug sensitivity, greater than 75 years of age, and renal impairment.(4,5) In an observational study, current use of a triple therapy with a diuretic, RAS inhibitor, and NSAID, was associated with an increased rate of acute kidney injury (rate ratio (RR) 1.31, 95% confidence interval (CI) 1.12-1.53). The highest risk of AKI associated with triple therapy were observed in the first 30 days of use (RR 1.82, CI 1.35-2.46). (6) Severe postural hypotension(1,2) and transient postural hypotension(3) has been reported in patients receiving concurrent captopril and furosemide. The effect is transient and may be more prevalent in patients who are sodium depleted.(8) Reversible renal failure(9) and decreased renal function(10) have been reported in patients receiving concurrent administration with enalapril and furosemide. In a study in which electrolytes were replaced with saline or Ringer's solution, no postural hypotension was noted; however, significant decreases in diastolic blood pressure occurred at three, four, and six hours after concurrent administration.(11)

Angiotensin Ii Receptor Block (Arb)/High-Dose Aspirin

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Angiotensin II receptor blockers (ARBs) can cause vasodilation of the efferent renal arteriole which may result in decreased glomerular filtration rate. NSAIDs inhibit prostaglandin synthesis which can lead to afferent arteriolar vasoconstriction and may negate any decrease in blood pressure.

CLINICAL EFFECTS: Concurrent use of aspirin may result in decreased antihypertensive effects of the ARB. In patients with existing renal impairment, the use of these agents may also result in further deterioration of renal clearance caused by renal hypoperfusion. Concurrent use of ARBs with aspirin and diuretics may result in increased risk of acute kidney injury (AKI).

PREDISPOSING FACTORS: Low water intake/dehydration, drug sensitivity, greater than 75 years of age, and use of diuretics can lead to hypovolemia and increased risk of AKI.

PATIENT MANAGEMENT: Monitor patients receiving doses of aspirin higher than 150 mg daily for decreased antihypertensive effects of their ARB. The use of alternative agents may need to be considered. Concurrent use of ARBs with aspirin and diuretics should be used with caution and monitored for signs of AKI.

DISCUSSION: In a population based cohort study, the concurrent use of NSAIDs with renin-angiotensin system (RAS) inhibitors in 5,710 hypertensive patients stabilized on antihypertensive therapy required hypertension treatment intensification. Adjusted hazard ratios (HR) for hypertension treatment intensification were 1.34 [95% CI 1.05-1.71] for NSAIDs in general, 1.79 (95% CI 1.15-2.78) for diclofenac and 2.02 (95% CI 1.09-3.77) for piroxicam. There were significant interactions between NSAIDs and angiotensin converting enzyme inhibitors (ACE inhibitors; HR 4.09, 95% CI 2.02-8.27) or angiotensin receptor blockers (ARBs; HR 3.62, 95% CI 1.80-7.31), but not with other antihypertensive drugs. In a computational study, the risk of AKI using triple therapy (combination of a diuretic, renin-angiotensin system (RAS) inhibitor, and NSAID) was assessed. The study found the following factors may increase an individual's susceptibility to AKI: low water intake, drug sensitivity, greater than 75 years of age, and renal impairment.(4,5) In an observational study, current use of a triple therapy combination was associated with an increased rate of acute kidney injury (rate ratio (RR) 1.31, 95% confidence interval (CI) 1.12-1.53). The highest risk of AKI associated with triple therapy were observed in the first 30 days of use (RR 1.82, CI 1.35-2.46).(6)

Angiotensin Ii Receptor Blocker (Arb)/K+ Sparing Diuretics

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Angiotensin II receptor blockers (ARBs) may decrease the renal excretion of potassium.

CLINICAL EFFECTS: Concurrent use of potassium sparing diuretics with an ARB may result in hyperkalemia.

PREDISPOSING FACTORS: Impaired renal function; diabetes mellitus.

PATIENT MANAGEMENT: Monitor serum potassium and adjust the dosage accordingly in patients receiving concurrent therapy with a potassium sparing diuretic and an ARB. In all patients taking eplerenone who start taking an an ARB, check serum potassium and creatinine levels after 3-7 days of concurrent therapy.

DISCUSSION: In a nested case-control study of heart failure patients receiving continuous ACE inhibitor/ARB therapy (n = 1,491,894), the risk of hyperkalemia was significantly associated with spironolactone use (odds ratio (OR) = 13.59; confidence interval (CI) = 11.63-15.88).(20) In a systemic literature review and meta-analysis of 20 randomized controlled studies, it was found that treatment with spironolactone and ACEI/ARB combination therapy compared to ACEI/ARB therapy alone increased the mean serum potassium concentration by 0.19 mEq/L (95% CI, 0.12-0.26 mEq/L).(21) A retrospective cohort study in patients with hypertension, diabetes, and albuminuria between 2008 and 2018 examined the efficacy and safety of mineralocorticoid receptor antagonists eplerenone and spironolactone in combination with ACEI/ARB compared to ACEI/ARB alone. Hyperkalemia was more frequent in combination therapy patients (n=1,282) versus monotherapy (n=5,484) (22.3 vs 10.9 per 100 person-years for combination and monotherapy, respectively; HR = 1.78, 95% CI: 1.42, 2.24).(22) Several studies have indicated that serum potassium levels increase when ACE inhibitors and ARB therapy is initiated and decrease when the drug is lowered. There are case reports of hyperkalemia during concurrent therapy with ARBs and spironolactone and with aliskiren and spironolactone. Based on this data, serum potassium levels should be monitored in patients receiving concomitant ARBs with potassium sparing diuretics.

Angiotensin Ii Receptor Blocker (Arb)/Nsaids; Salicylates

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Angiotensin II receptor blockers (ARBs) can cause vasodilation of the efferent renal arteriole which may result in decreased glomerular filtration rate. NSAIDs inhibit prostaglandin synthesis which can lead to afferent arteriolar vasoconstriction and may negate any decrease in blood pressure.

CLINICAL EFFECTS: Concurrent use of ARBs with NSAIDs may result in decreased antihypertensive effects. In patients with existing renal impairment, the use of these agents together may also result in further deterioration of renal clearance caused by renal hypoperfusion. Concurrent use of ARBs with NSAIDs and diuretics may result in increased risk of acute kidney injury (AKI).

PREDISPOSING FACTORS: Low water intake/dehydration, drug sensitivity, greater than 75 years of age, and use of diuretics can lead to hypovolemia and increased risk of AKI.

PATIENT MANAGEMENT: Patients maintained on ARBs should be monitored for a loss of blood pressure control and a change in renal function if an NSAID is added to their regimen. Patients receiving concurrent therapy may require higher doses of ARBs. If blood pressure control cannot be achieved or if the patient's renal function deteriorates, the NSAID may need to be discontinued. Patients should be monitored for hypotension if NSAIDs are withdrawn from concurrent ARB therapy. Concurrent use of ARBs with NSAIDs and diuretics should be used with caution and monitored for signs of AKI.

DISCUSSION: In a computational study, the risk of AKI using triple therapy (combination of a diuretic, renin-angiotensin system (RAS) inhibitor, and NSAID) was assessed. The study found the following factors may increase an individual's susceptibility to AKI: low water intake, drug sensitivity, greater than 75 years of age, and renal impairment.(22,23) In an observational study, current use of a triple therapy combination was associated with an increased rate of acute kidney injury (rate ratio (RR) 1.31, 95% confidence interval (CI) 1.12-1.53). The highest risk of AKI associated with triple therapy were observed in the first 30 days of use (RR 1.82, CI 1.35-2.46).(24) In a population based cohort study, the concurrent use of NSAIDs with renin-angiotensin system (RAS) inhibitors in 5,710 hypertensive patients stabilized on antihypertensive therapy required hypertension treatment intensification. Adjusted hazard ratios (HR) for hypertension treatment intensification were 1.34 [95% CI 1.05-1.71] for NSAIDs in general, 1.79 (95% CI 1.15-2.78) for diclofenac and 2.02 (95% CI 1.09-3.77) for piroxicam. There were significant interactions between NSAIDs and angiotensin converting enzyme inhibitors (ACE inhibitors; HR 4.09, 95% CI 2.02-8.27) or angiotensin receptor blockers (ARBs; HR 3.62, 95% CI 1.80-7.31), but not with other antihypertensive drugs.

Angiotensin Ii Receptor Blocker (Arb)/Potassium Supplements

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Angiotensin II receptor blockers (ARBs) may decrease the renal excretion of potassium.

CLINICAL EFFECTS: Concurrent use of potassium supplements with ARBs may result in hyperkalemia.

PREDISPOSING FACTORS: Impaired renal function; diabetes mellitus.

PATIENT MANAGEMENT: Monitor serum potassium and adjust the dosage accordingly in patients receiving concurrent therapy with potassium supplements and ARBs.

DISCUSSION: Several studies have indicated that serum potassium levels increase when ARB therapy is initiated and decrease when the drug is lowered. Based on this data, serum potassium levels should be monitored in patients receiving potassium supplements with ARBs.

Selected Antihypertensive Agents/Selected Maois

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Both MAOIs and antihypertensive agents may increase the risk of postural hypotension.(1,2)

CLINICAL EFFECTS: Postural hypotension may occur with concurrent therapy of MAOIs and antihypertensive agents.(1,2)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer of phenelzine states all patients should be followed closely for symptoms of postural hypotension. Hypotensive side effects have occurred in patients who have been hypertensive and normotensive, as well as hypotensive at initiation of phenelzine.(1) The manufacturer of tranylcypromine states hypotension has been observed most commonly but not exclusively in patients with pre-existing hypertension. Tranylcypromine doses greater than 30 mg daily have a major side effect of postural hypotension and can lead to syncope. Gradual dose titration is recommended to decrease risk of postural hypotension. Combined use with other agents known to cause hypotension have shown to have additive side effects and should be monitored closely.(2) Monitor the patient for signs and symptoms of postural hypotension including dizziness, lightheadedness, or weakness, especially upon standing. Monitor blood pressure as well as orthostatic vitals and adjust antihypertensive therapy, including decreasing the dose, dividing doses, or scheduling doses at bedtime, as needed to maintain goal blood pressure. If blood pressure remains hypotensive, consider decreasing the dose of phenelzine or tranylcypromine. In some cases, discontinuation of one or both agents may be necessary.(3) Normotensive patients on stable antihypertensive therapy who are started on either phenelzine or tranylcypromine may be at increased risk for hypotension. Hypertensive patients on stable phenelzine or tranylcypromine who require antihypertensive therapy would be at decreased risk for hypotension.

DISCUSSION: A review article describes the pharmacology of phenelzine and tranylcypromine as non-selective MAOIs which inhibit both type A and type B substrates. Orthostatic hypotension is described as the most common MAOI side effect and usually occurs between initiation and the first 3-4 weeks of therapy.(3) In a double-blind study, 71 patients were randomized to receive a 4-week trial of either tranylcypromine, amitriptyline, or the combination. The number of patients reporting dizziness at 4 weeks was not different between the three treatment groups (tranylcypromine 52.4%; amitriptyline 65%; combination 66.7%). Blood pressure (BP) assessment noted a significant drop in standing BP in the tranylcypromine group compared to baseline (systolic BP change = -10 mmHg; p<0.02 and diastolic BP change = -9 mmHg; p<0.02). Combination therapy also had a significant drop in standing BP compared to baseline (systolic BP change = -9 mmHg; p<0.02). Patients receiving amitriptyline had no significant change in BP from baseline at 4 weeks. All three groups had a trend toward increasing orthostatic hypotension in BP changes from lying to standing. The change in orthostatic hypotension was significant in the amitriptyline group with an average systolic BP orthostatic drop of -9 mmHg (p<0.05).(4) A randomized, double-blind study of 16 inpatients with major depressive disorder were treated with either phenelzine or tranylcypromine. Cardiovascular assessments were completed at baseline and after 6 weeks of treatment. After 6 weeks, 5/7 patients (71%) who received phenelzine had a decrease in standing systolic BP greater than 20 mmHg from baseline. Head-up tilt systolic and diastolic BP decreased from baseline in patients on phenelzine (98/61 mmHg v. 127/65 mmHg, respectively; systolic change p=0.02 and diastolic change p=0.02). After 6 weeks, 6/9 patients (67%) who received tranylcypromine had a decrease in standing systolic BP greater than 20 mmHg from baseline. Head-up tilt systolic and diastolic BP decreased from baseline in patients on tranylcypromine (113/71 mmHg v. 133/69 mmHg, respectively; systolic change p=0.09 and diastolic change p=0.07).(5) Selected MAOIs linked to this monograph include: phenelzine and tranylcypromine. Selected antihypertensive agents include: ACE inhibitors, alpha blockers, ARBs, beta blockers, calcium channel blockers, aprocitentan, clonidine, hydralazine, moxonidine, and sparsentan.

Selected Antihypertensives And Vasodilators/Apomorphine

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Apomorphine causes dose-dependent decreases in blood pressure. Concurrent use with antihypertensive agents may result in additive effects on blood pressure.(1)

CLINICAL EFFECTS: Concurrent use of antihypertensives and apomorphine may result in orthostatic hypotension with or without dizziness, nausea, or syncope.(1)

PREDISPOSING FACTORS: The risk of orthostatic hypotension may be increased during dose escalation of apomorphine and in patients with renal or hepatic impairment.(1)

PATIENT MANAGEMENT: Patients receiving concurrent therapy should be monitored for hypotension. Counsel patients about the risk of orthostatic hypotension.(1)

DISCUSSION: Healthy volunteers who took sublingual nitroglycerin (0.4 mg) concomitantly with apomorphine experienced a mean largest decrease in supine systolic blood pressure (SBP) of 9.7 mm Hg and in supine diastolic blood pressure (DBP) of 9.3 mm Hg, and a mean largest decrease in standing SBP and DBP of 14.3 mm Hg and 13.5 mm Hg, respectively. The maximum decrease in SBP and DBP was 65 mm Hg and 43 mm Hg, respectively. When apomorphine was taken alone, the mean largest decrease in supine SBP and DBP was 6.1 mm Hg and 7.3 mm Hg, respectively, and in standing SBP and DBP was 6.7 mm Hg and 8.4 mm Hg, respectively.(1)

Selected Antihypertensives/Tizanidine

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Tizanidine is an alpha-2 agonist. Concurrent use with antihypertensive agents may result in additive effects on blood pressure.(1)

CLINICAL EFFECTS: Concurrent use of antihypertensives and tizanidine may result in hypotension.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Patients receiving concurrent therapy should be monitored for hypotension. The risk of hypotension may be decreased by careful titration of tizanidine dosages and monitoring for hypotension prior to dose advancement. Counsel patients about the risk of orthostatic hypotension.(1)

DISCUSSION: Severe hypotension has been reported following the addition of tizanidine to existing lisinopril therapy.(2-4)

Selected Arbs/Paritaprevir-Ritonavir

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: The combination of paritaprevir-ritonavir inhibits multiple transport or elimination pathways: OATP1B1, OATP1B3, OATP2B1, P-gp, BCRP, CYP3A4 and UGT1A1.(1-3) Selected angiotensin receptor blockers(ARBs) - candesartan, losartan, olmesartan, telmisartan and valsartan are substrates for one or more of these pathways.(1,2,4-8)

CLINICAL EFFECTS: Transport inhibition of candesartan, losartan, olmesartan, telmisartan, or valsartan may lead to higher systemic concentrations, increasing the risk for hypotension or renal impairment.(1)

PREDISPOSING FACTORS: Patients with renal impairment or dehydration are more susceptible to adverse effects from angiotensin receptor blockers(ARBs).(1)

PATIENT MANAGEMENT: The manufacturer of paritaprevir-ritonavir(1,2) recommends reducing the angiotensin receptor blocker (ARB) dose when this hepatitis C therapy is started. Monitor for hypotension and/or change in renal function. Further decreases in the ARB dose may be necessary.

DISCUSSION: The interaction between ARBs and paritaprevir-ritonavir has not been studied.(1,2) In vitro studies have found that OATP1B1 and/or OATP1B3 transports olmesartan,(4,5) telmisartan(6,7) and valsartan(8) into the liver for further metabolism or elimination. Inhibition of transport leads to increased systemic concentrations of the ARB. Due to the lack of in vivo studies, the magnitude of this effect is not clear.

*Known hypersensitivity to losartan or any ingredient in the formulation.

*Concomitant therapy with aliskiren in patients with diabetes mellitus.

• Pregnancy

• Child-pugh class B hepatic impairment
• Disease of liver
• Hyperkalemia
• Hyponatremia
• Hypotension
• Hypovolemia
• Renal artery stenosis

• Kidney disease with reduction in glomerular filtration rate (GFr)

Adverse effects occurring in at least 2% of patients with hypertension receiving losartan, and at a higher incidence than with placebo, include dizziness, upper respiratory infection, nasal congestion, and back pain.

Less Frequent

• Chest pain

Rare or Very Rare

• Abnormal hepatic function tests
• Anaphylaxis
• Angioedema
• Hepatitis
• Hyperkalemia
• Hyponatremia
• IgA vasculitis
• Interstitial nephritis
• Intestinal angioedema
• Rhabdomyolysis
• Thrombocytopenic disorder
• Vasculitis

More Frequent

• Back pain
• Dizziness
• Headache disorder
• Muscle weakness
• Nasal congestion
• Upper respiratory infection

Less Frequent

• Anorexia
• Diarrhea
• Dyspepsia
• Edema
• Fatigue
• Hypoglycemic disorder
• Hypotension
• Nausea
• Orthostatic hypotension
• Pharyngitis
• Urinary tract infection

Rare or Very Rare

• Acute abdominal pain
• Cough
• Cramps
• Dysgeusia
• Erythema
• Insomnia
• Malaise
• Myalgia
• Sialoadenitis
• Sinusitis

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Antihypertensive effects of losartan have been established in hypertensive pediatric patients 6-16 years of age.

Safety and efficacy of losartan in pediatric patients <6 years of age and pediatric patients with glomerular filtration rate <30 mL/minute per 1.73 m2 have not been established.

Losartan can cause fetal harm when administered to a pregnant woman. Use of drugs that act on the RAS during the second or third trimester of pregnancy reduces fetal renal function and increases fetal and neonatal morbidity and death. Oligohydramnios in pregnant women who use drugs affecting the RAS in the second or third trimester of pregnancy can result in reduced fetal renal function leading to anuria and renal failure, fetal lung hypoplasia, skeletal deformations (including skull hypoplasia), hypotension, and death.

Discontinue losartan immediately when pregnancy is detected. In the rare case that there is no appropriate alternative therapy, apprise the mother of the potential risk to the fetus. If losartan is taken during pregnancy, perform serial ultrasound examinations to assess the intra-amniotic environment; if oligohydramnios is observed, discontinue losartan, unless it is considered life-saving for the mother. Oligohydramnios may not appear until after the fetus has sustained irreversible injury. Closely observe neonates who have been exposed to losartan in utero for signs of hypotension, oliguria, and hyperkalemia. If oliguria or hypotension occurs, support blood pressure and renal perfusion. Exchange transfusions or dialysis may be required.

Losartan is distributed into milk in rats; it is not known whether the drug is distributed into human breast milk. A decision should be made whether to discontinue breastfeeding or discontinue the drug, taking into account the potential risk in breastfeeding infants and the importance of the drug to the mother.

The manufacturer makes no specific dosage recommendations for geriatric patients.

In controlled clinical trials evaluating losartan for hypertension, 19% of patients were >=65 years of age and 2% were >=75 years of age. In controlled clinical trials evaluating losartan for renal protection in type 2 diabetes, 33% of patients were >=65 years of age. In controlled clinical trials evaluating losartan for the reduction of cardiovascular death, stroke, and myocardial infarction in hypertensive patients with left ventricular hypertrophy, 62% of patients were >=65 years of age and 18% were >=75 years of age. No overall differences in pharmacokinetics, safety, or efficacy of losartan have been observed between geriatric patients and younger adults, but increased sensitivity in some older individuals cannot be ruled out.