7 DRUG INTERACTIONS
Table 2 includes clinically significant drug interactions with doxercalciferol.
| Drugs that May Increase the risk of Hypercalcemia | |
| Clinical Impact | Concomitant administration of high doses of calcium-containing preparations or other vitamin D compounds may increase the risk of hypercalcemia. Thiazide diuretics are known to induce hypercalcemia by reducing excretion of calcium in the urine. |
| Examples | Calcium-containing products, other vitamin D compounds or thiazide diuretics |
| Intervention | Monitor serum calcium concentrations more frequently and adjust Doxercalciferol Injection dose as needed [see Warnings and Precautions (5.1)]. |
| Digitalis Compounds | |
| Clinical Impact | Doxercalciferol can cause hypercalcemia which can potentiate the risk of digitalis toxicity. |
| Intervention | Monitor patients for signs and symptoms of digitalis toxicity and increase frequency of serum calcium monitoring when initiating or adjusting the dose of Doxercalciferol Injection in patients receiving digitalis compounds [see Warnings and Precautions (5.2)]. |
| Cytochrome P450 Inhibitors | |
| Clinical Impact | Doxercalciferol is activated by CYP 27 in the liver. Cytochrome P450 inhibitors may inhibit the 25-hydroxylation of doxercalciferol and thus reduce the formation of active doxercalciferol moiety [see Clinical Pharmacology (12.3)]. |
| Examples | Ketoconazole and erythromycin |
| Intervention | If a patient initiates or discontinues therapy with a cytochrome P450 inhibitor, dose adjustment of Doxercalciferol Injection may be necessary. Monitor intact PTH and serum calcium concentrations closely. |
| Enzyme Inducers | |
| Clinical Impact | Doxercalciferol is activated by CYP 27 in the liver. Enzyme inducers may affect the 25-hydroxylation of doxercalciferol [see Clinical Pharmacology (12.3)]. |
| Examples | Glutethimide and phenobarbital |
| Intervention | If a patient initiates or discontinues therapy with an enzyme inducer, dose adjustment of Doxercalciferol Injection may be necessary. Monitor intact PTH and serum calcium concentrations closely. |
| Magnesium-containing Products | |
| Clinical Impact | Concomitant administration of Doxercalciferol Injection and high doses of magnesium-containing products may increase the risk of hypermagnesemia. |
| Examples | Magnesium-containing products such as antacids |
| Intervention | Avoid use of magnesium-containing products and Doxercalciferol Injection. |