Thalidomide is not a substrate for cytochrome P450 (CYP450) isoenzymes and does not inhibit or induce human CYP450 enzymes in vitro. Therefore, pharmacokinetic drug-drug interactions are not anticipated when thalidomide is coadministered with drugs that are substrates, inhibitors or inducers of cytochrome P450.
Opioids, Antihistamines, Antipsychotics, Anti-anxiety Agents, or Other CNS Depressants (Including Alcohol)
The use of opioids, antihistamines, antipsychotics, anti-anxiety agents, or other CNS depressants concomitantly with THALOMID may cause an additive sedative effect and should be avoided.
Drugs which Cause Bradycardia
The use of drugs which slow cardiac conduction concomitantly with THALOMID may cause an additive bradycardic effect and should be used with caution. Cardiovascular medications which may cause bradycardia include calcium channel blockers, beta blockers, alpha/beta-adrenergic blockers, and digoxin. Non-cardiac drugs that may cause bradycardia include H2 blockers (e.g., famotidine, cimetidine), lithium, tricyclic antidepressants and neuromuscular blockers (succinylcholine).
In 16 healthy men, the pharmacokinetic profile of a single 0.5 mg digoxin dose was similar with and without the coadministration of thalidomide 200 mg/day at steady state levels. The single dose of digoxin had no effect on the pharmacokinetic profile of thalidomide. The safety of long-term concomitant use of THALOMID and digoxin has not been evaluated.
Drugs which Cause Peripheral Neuropathy
The use of drugs which cause peripheral neuropathy (e.g., bortezomib, amiodarone, cisplatin, docetaxel, paclitaxel, vincristine, disulfiram, phenytoin, metronidazole, alcohol) can cause an additive effect and should be used with caution.
Hormonal contraceptives increase the risk of thromboembolism. It is not known whether concomitant use of hormonal contraceptives further increases the risk of thromboembolism with THALOMID.
In 10 healthy women, the pharmacokinetic profiles of norethindrone and ethinyl estradiol following administration of a single dose containing 1.0 mg of norethindrone acetate and 75 µg of ethinyl estradiol were studied. The results were similar with and without coadministration of thalidomide 200 mg/day to steady-state levels.
In 13 healthy men, the pharmacokinetic profile and international normalized ratio (INR) of prothrombin time for warfarin, following a single oral dose of 25 mg, were similar with and without the coadministration of thalidomide 200 mg/day at steady-state levels. The single dose of warfarin had no effect on the pharmacokinetic profile of thalidomide.
Drugs that Interfere with Hormonal Contraceptives
Concomitant use of HIV-protease inhibitors, griseofulvin, modafinil, penicillins, rifampin, rifabutin, phenytoin, carbamazepine, or certain herbal supplements such as St. John’s Wort with hormonal contraceptive agents may reduce the effectiveness of the contraception up to one month after discontinuation of these concomitant therapies. Therefore, females requiring treatment with one or more of these drugs must use two OTHER effective or highly effective methods of contraception while taking thalidomide.
Concomitant Therapies that may Increase the Risk of Thromboembolism
Erythropoietic agents, or other agents that may increase the risk of thromboembolism, such as estrogen containing therapies, should be used with caution in multiple myeloma patients receiving thalidomide with dexamethasone [see Warnings and Precautions].