Dosoquin (cholecalciferol (vit D3)/vitamin K2)

Dietary intake of ergocalciferol and cholecalciferol varies among individual patients, and dietary intake should always be considered when calculating the appropriate dosage of vitamin D analogs. During therapy with vitamin D analogs, dosage depends on the nature and severity of the patient's hypocalcemia and must be individualized to maintain serum calcium concentrations of 9-10 mg/dL. In the management of hypoparathyroidism, pseudohypoparathyroidism, and familial hypophosphatemia, the range between therapeutic and toxic effects is narrow; however, hypercalcemia may occur at any time when therapeutic doses of vitamin D analogs are used, and careful monitoring is imperative. In the management of secondary hyperparathyroidism, dosage of vitamin D analogs should be individualized according to serum or plasma intact parathyroid hormone (iPTH) concentrations and serum calcium and phosphorus concentrations.

During therapy with vitamin D analogs, patients should receive adequate amounts of calcium through management of diet or administration of calcium supplements; however, overdosage of calcium may lead to hypercalcemia. Dosage of vitamin D analogs should be decreased when symptoms improve and before biochemical normality or complete bone healing has occurred because requirements for vitamin D analogs often decrease after bone healing occurs. In patients who become bedridden (especially children), dosage reduction may occasionally be needed to avoid hypercalcemia.

Vitamin D analogs are usually administered orally; however, calcitriol, doxercalciferol, and paricalcitol may be given by IV injection. Ergocalciferol may be given by IM injection; however, a suitable formulation of the drug for IM injection no longer is commercially available in the US.

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There are no contraindication interactions for this drug.

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

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)

Vitamin K/Selected Anticoagulants (Vitamin K Antagonists)

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

MECHANISM OF ACTION: Anticoagulants interfere with the activation of vitamin K-dependent clotting factors. Vitamin K administration may reverse this effect.

CLINICAL EFFECTS: The pharmacological effect of anticoagulants may be reversed resulting in thrombus formation.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Patients receiving anticoagulants should avoid eating unusual increases in foods high in vitamin K content. The time of highest risk for a coumarin-type drug interaction is when the precipitant drug is initiated or discontinued. Contact the prescriber before initiating, altering the dose or discontinuing either drug.

DISCUSSION: Numerous reports have demonstrated that vitamin K interferes with the hypoprothrombinemic effects of anticoagulants. However, reports of clinically important consequences are uncommon. A clearer understanding of the mechanism by which these drugs act has made it possible to use vitamin K to control bleeding side effects of warfarin therapy. One should be aware of the vitamin K content of enteral feeding products being administered to patients on anticoagulant therapy. Prothrombin time should be monitored when these products are given.

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

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)

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• Hypervitaminosis D

• Hypercalcemia
• Hyperphosphatemia
• Kidney stone

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

There is no enhanced messaging for this drug.

There are no severe adverse reactions for this drug.

There are no less severe adverse reactions for this drug.

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A characteristic physiognomy, possibly with aortic valvular stenosis, retinopathy, and mental and/or physical retardation, has occurred following prolonged hypercalcemia in infants and in neonates of mothers with hypercalcemia during pregnancy. Hypercalcemia during pregnancy may also lead to suppression of PTH concentrations in the neonate resulting in hypocalcemia, tetany, and seizures. Safe use of calcifediol, calcitriol, dihydrotachysterol (no longer commercially available in the US), paricalcitol, or ergocalciferol during pregnancy has not been established; however, the risks to the mother and fetus from untreated hypoparathyroidism or hypophosphatemia may be greater than those resulting from administration of vitamin D analogs.

Safe use of calcifediol, calcitriol, dihydrotachysterol, doxercalciferol, paricalcitol, or ergocalciferol during lactation has not been established; however, the risks to the mother and fetus from untreated hypoparathyroidism or hypophosphatemia may be greater than those resulting from administration of vitamin D analogs. Large doses of vitamin D analogs should not be administered to nursing women.

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