Children's Chewable Multivitmn (pediatric multivitamin no.25/folic acid)

Dosage of folic acid injection (sodium folate) is expressed in terms of folic acid. In general, although patient response to folic acid therapy depends on the degree and nature of the deficiency, once proper corrective measures are undertaken, folate-deficient patients generally respond rapidly. During the first 24 hours of treatment, the patient experiences an improved sense of well-being, and within 48 hours, the bone marrow begins to become normoblastic. Reticulocytosis generally begins within 2-5 days following initiation of folic acid therapy.

Folic acid is usually administered orally. When oral administration is not feasible or when malabsorption is suspected, the drug may be administered by deep IM, subcutaneous, or IV injection. However, most patients with malabsorption are able to absorb oral folic acid.

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In folate-deficient patients, folic acid therapy may increase phenytoin metabolism, resulting in decreased phenytoin serum concentrations. Although this interaction is not usually clinically important, an increase in seizure frequency may occur in some patients.

It has been reported that concurrent administration of chloramphenicol and folic acid in folate-deficient patients may result in antagonism of the hematopoietic response to folic acid. Although the importance and mechanism of the interaction is unclear, the hematologic response to folic acid in patients receiving both drugs should be carefully monitored.

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

Vitamin A/Selected Retinoids

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: The retinoids are structurally related to vitamin A. (1-6)

CLINICAL EFFECTS: Concurrent use of retinoids with vitamin A supplements may result in signs of vitamin A toxicity.(1-6) Symptoms of vitamin A toxicity include nausea, vomiting, loss of appetite, weakness, dry or itchy skin or lips, irritability, and hair loss.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer of acitretin states that concomitant use of vitamin A supplements should be avoided.(1) The manufacturer of bexarotene states that patients should be advised to limit vitamin A supplements. In clinical studies, patients were advised to limit their vitamin A intake to less than or equal to 15,000 International Units/day.(2) The manufacturer of isotretinoin states that patients should be advised against taking vitamin A supplements.(3) The manufacturer of palovarotene states that concomitant use of vitamin A must be avoided.(4) The manufacturer of tretinoin states that tretinoin must not be administered in combination with vitamin A.(5) The UK manufacturer of alitretinoin states that tretinoin must not be administered in combination with vitamin A.(6)

DISCUSSION: The retinoids are structurally related to vitamin A. The concurrent use of retinoids with vitamin A may result in signs and symptoms of vitamin A toxicity.(1-6)

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

Folic Acid/Fluorouracil & Fluorouracil Prodrugs

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

MECHANISM OF ACTION: Folic acid has been shown to enhance both the therapeutic and toxic effects of fluoropyrimidines, such as 5-fluorouracil (5-FU) and fluorouracil prodrugs.(1-3) Fluorouracil prodrugs include capecitabine and tegafur.

CLINICAL EFFECTS: Folic acid, when used concurrently with 5-FU or fluorouracil prodrugs, has been shown to increase side effects of 5-FU.(1-3)

PREDISPOSING FACTORS: Patients who are intermediate or poor dihydropyrimidine dehydrogenase (DPYD) metabolizers have diminished or no DPYD function. Since DPYD is the rate-limiting enzyme involved in fluoropyrimidine metabolism, these patients may be more susceptible to the effects of this interaction.(3)

PATIENT MANAGEMENT: Folic acid or folate analog-containing products should not be used concurrently with fluorouracil or fluorouracil prodrugs unless directed by the healthcare provider.(1-3) Fluorouracil prodrugs include capecitabine and tegafur.

DISCUSSION: Due to increased toxic effects, stomatitis and diarrhea are observed more commonly, may be more severe, and may occur for a prolonged duration when compared to therapy with 5-FU alone. It is postulated that the lower standard dose of 5-FU in the US versus other regions may be due to increased folic acid supplementation within the US food supply.(2) In a cohort study in 290 patients, the use of dietary supplements with folic acid during treatment compared to nonuse increased the risk of capecitabine toxicities (HR 1.81, 95%CI: 1.15,2.85). The detection of folic acid in plasma also increased the risk of capecitabine toxicities (HR 2.09, 95%CI: 1.24,3.52 and HR 2.31, 95%CI: 1.29,4.13 at diagnosis and during treatment, respectively).(4) In a cohort study of 9 patients, patients taking folate-containing supplements and higher serum folate levels had an increased risk of grade >=2 toxicity. The risk of grade >=2 toxicity increased by 9% for every increase in serum folate level by 10 nmol/L. Patients with grade >=2 toxicity had higher serum folate levels than patients with grade <= 1 toxicity (28 nmol/L [range, 13.2-45.4] vs. 20 nmol/L [range, 12.8-45.4]; p=0.001).(5) In two case reports, patients developed capecitabine toxicity while taking supplements containing folic acid 400-500 mcg.(6) In a case report, a woman developed grade 4 diarrhea, grade 3 vomiting, and grade 3 hand-foot syndrome 8 days after the addition of capecitabine (2500 mg/m2/day) to high-dose folic acid supplementation. She developed necrotic colitis and died, despite the discontinuation of folic acid and capecitabine.(7) There are two other reports of excessive fluorouracil toxicity in patients treated with folic acid.(8)

Serum Phosphate Level-Altering Drugs/Erdafitinib

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

MECHANISM OF ACTION: Medications that alter serum phosphate may interfere with interpretation of phosphate levels that are needed to determine initial erdafitinib dose.(1)

CLINICAL EFFECTS: Serum phosphate levels that are elevated by concomitant medications may result in an inappropriately low dose and decreased effectiveness of erdafitinib. Serum phosphate levels that are decreased by concomitant medications may result in an inappropriately high dose and increased toxicity from erdafitinib.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer of erdafitinib states that agents that alter serum phosphate levels should be avoided before the initial dose increase period for erdafitinib based on serum phosphate levels (days 14 to 21).(1)

DISCUSSION: Concomitant administration of serum phosphate level-altering agents during the initial dose increase period of erdafitinib based on serum phosphate levels (days 14 to 21) may interfere with serum phospate levels and lead to incorrect dosing of erdafitinib.(1) Agents that may alter serum phosphate levels linked to this monograph include: aluminum carbonate, aluminum hydroxide, calcium acetate, calcium carbonate, calcium citrate, cod liver oil, ferric citrate, lanthanum, magnesium carbonate, magnesium hydroxide, potassium phosphate, sevelamer, sodium phosphate, sucroferric oxyhydroxide, tenapanor, and vitamin D.(1)

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

Ascorbic Acid (Vitamin C)/Deferoxamine

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

MECHANISM OF ACTION: It is believed that ascorbic acid increases the iron available for chelation from an labile intracellular iron pool. Ascorbic acid may then facilitate iron-induced oxidative tissue damage.(1)

CLINICAL EFFECTS: Dietary ascorbic acid may increase the absorption of dietary iron. Supplemental ascorbic acid therapy given during chelation therapy may improve iron output;(1-9) however, excessive dosages may result in cardiac toxicity from iron-induced oxidative tissue damage.(1,2,11-13)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Ascorbic acid intake is often restricted in patients with iron overload; however, it has been used in conjunction with deferoxamine to increase iron excretion.(2) Supplemental ascorbic acid therapy should only be initiated after one month of deferoxamine therapy. Ascorbic acid therapy should only be given in patients receiving deferoxamine regularly and the dose should be given after the infusion has started. The dosage of ascorbic acid should be limited to 50 mg daily in children under 10 years of age; 100 mg daily in older children; and 200 mg daily, in divided doses, in adults.(2) Cardiac function should be monitored in patients receiving concurrent therapy. Discontinue ascorbic acid therapy in patients who develop cardiac dysfunction.(2)

DISCUSSION: Supplemental ascorbic acid therapy given during chelation therapy has been shown to improve iron output,(1-9) possibly by increasing iron available for chelation from an labile intracellular iron pool.(1) However, dosages in excess of 500 mg daily have been associated with cardiac dysfunction.(1,2,11-13)

Fat Soluble Vitamins/Colesevelam

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

MECHANISM OF ACTION: Colesevelam may decrease the absorption of fat-soluble vitamins A, D, E, and K.(1)

CLINICAL EFFECTS: Colesevelam may reduce absorption of fat soluble vitamins, leading to a deficiency state.

PREDISPOSING FACTORS: A pre-existing deficiency of fat soluble vitamins (A,D,E and K) or chronic malabsorption syndrome.

PATIENT MANAGEMENT: The inhibition of fat soluble vitamin absorption by colesevelam should be borne in mind during implementation of a vitamin supplementation strategy. Oral multivitamin supplements should be taken at least four hours before the dose of colesevelam.(1)

DISCUSSION: Colesevelam may decrease the absorption of fat-soluble vitamins A, D, E, and K.(1)

Fat Soluble Vitamins/Orlistat

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

MECHANISM OF ACTION: The acetate ester forms of vitamin A and vitamin E must undergo hydrolysis for absorption from the gastrointestinal tract.(1) The enzyme responsible for this hydrolysis is inhibited by orlistat.(2)

CLINICAL EFFECTS: Orlistat may reduce absorption of fat soluble vitamins, leading to a deficiency state.

PREDISPOSING FACTORS: A pre-existing deficiency of fat soluble vitamins (A,D,E and K) or chronic malabsorption syndrome.

PATIENT MANAGEMENT: The inhibition of fat soluble vitamin absorption by orlistat should be borne in mind during implementation of a vitamin supplementation strategy. Patients should be strongly encouraged to take a multivitamin supplement which contains fat soluble vitamins, particularly Vitamin D as it appears most susceptible to this interaction.(4,5) Multivitamin supplements should be taken at least two hours before or after the dose of orlistat, or at bedtime.(4) Patients with chronic malabsorption syndromes should not receive orlistat.(4)

DISCUSSION: Adult patients taking orlistat without supplementation showed a greater reduction in vitamin A,D,E and beta-carotene levels compared to placebo during two or more consecutive visits in studies of 1-2 years duration; these patients had normal baseline values prior to orlistat therapy. Low vitamin values in orlistat patients were as follows: low Vitamin D 12%, low beta-carotene 6.1%, low Vitamin E 5.8%, low Vitamin A 2.2%.(4) A pharmacokinetic interaction study showed a 30% reduction in beta-carotene supplement absorption and a 60% decreased in vitamin E acetate absorption with concomitant orlistat.(4) In a study, orlistat produced the vitamin net concentration by approximately 43%.(1) In a study, no statistically significant decrease in vitamin A absorption was observed with concurrent orlistat.(2) In a study, mean vitamin D levels were significantly reduced compared with baseline after one month of orlistat therapy despite multivitamin supplementation.(5)

Folic Acid/Pafolacianine

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

MECHANISM OF ACTION: Folate, folic acid, and folate-containing supplements may reduce binding of pafolacianine to folate receptors expressed on ovarian cancer cells.

CLINICAL EFFECTS: Folate, folic acid, and folate-containing supplements could reduce the detection of malignant lesions with pafolacianine.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Avoid administration of folate, folic acid, or folate-containing supplements within 48 hours before administration of pafolacianine.

DISCUSSION: Folate, folic acid, and folate-containing supplements may reduce binding of pafolacianine to folate receptors expressed on cancer cells, which could result in reduced detection of malignant lesions with pafolacianine.

Folic Acid; Pyrimethamine/Hydantoins

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

MECHANISM OF ACTION: Unknown, but probably involves altered metabolism of the hydantoin.

CLINICAL EFFECTS: May observe decreased effectiveness of hydantoin, resulting in loss of seizure control.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: If both drugs are administered, monitor both the hydantoin plasma levels as well as the seizure control of the patient. Adjust the dose of hydantoin accordingly.

DISCUSSION: The effects of an interaction are not expected to occur in the majority of patients. Discontinuation of folic acid has caused phenytoin levels to increase in patients who experienced a decrease in phenytoin levels when folic acid was started. Monitor these patients for hydantoin toxicity. Signs and symptoms of hydantoin toxicity include ataxia, nystagmus and involuntary movements.

Thiamine/Patiromer

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

MECHANISM OF ACTION: Patiromer may bind to thiamine.(1)

CLINICAL EFFECTS: Concurrent use may result in decreased gastrointestinal absorption and loss of efficacy of thiamine.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of patiromer recommends administering patiromer at least 3 hours before or 3 hours after thiamine.(1)

DISCUSSION: An in vitro binding study found potentially clinically significant binding of thiamine by patiromer. It is recommended to take these drugs 3 hours apart.(1)

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• Leber's hereditary optic atrophy

There are no severe contraindications for this drug.

• Atrophic gastritis
• Hypokalemia
• Increased risk of bleeding due to coagulation disorder
• Vitamin K deficiency induced hypoprothrombinemia

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Rare or Very Rare

• Bronchospastic pulmonary disease
• Concentration difficulty

Rare or Very Rare

• Abdominal distension
• Acute cognitive impairment
• Anorexia
• Depression
• Dysgeusia
• Erythema
• Excitement
• Flatulence
• Irritability
• Malaise
• Nausea
• Pruritus of skin
• Skin rash
• Sleep disorder

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