Cyclophosphamide drug interactions

The following drug classes may have a potential drug interaction with nevirapine Antiarrhythmics, anticonvulsants, antifungals, calcium channel blockers, cancer chemotherapy (cyclophosphamide), ergot alkaloids, immunosuppressants, motility agents, opiate agonists. 

The calcium channel blocker mibefradil (Posicor ) was removed from the market in 1998. The headline for the Pink Sheets article describing this action was "Posicor Withdrawal Reflects Complexity of Interaction Profile" (59). Products identified as potentially dangerous in combination with mibefradil included cardiac drugs, such as amiodarone, flecainide, and propafenone oncologic products, such as tamoxifen, cyclophosphamide, etoposide, ifosfamide, and vinblastine and the immunosuppressant medications cyclosporine and tacrolimus. The sponsor s decision to withdraw mibefradil was based on the complexity of the drug interaction information that would have to be communicated to ensure safe usage. 

Pin MN, Renton K, Crocker JFS, Acott PD. A proposed drug interaction leadii to cyclophosphamide-induced encephalopathy. PecSatrRes (2002) 51,437A. 

Incompatibilities of metoclopramide depend on drug concentration, pH, and temperature. It is incompatible with cephalosporins, chloramphenicol, sodium bicarbonate, doxorubicin, cisplatin, and cyclophosphamide. Caution should be exercised with simultaneous administration of metoclopramide with lithium, sym-pathomimetics, antidepressants, bromocriptine, and carbamazepine. Omperazole interacts with tolbutamide, clarithromycin, and phenytoin. Coadministration of rantidine and cisapride increases the plasma concentration of rantidine. Abuse of senna laxative has been reported and may cause hepatitis.176-178... 

A retrospective study in 22 children with cancers addressed the potential interaction between fluconazole and cyclophosphamide. Children with an established profile of cyclophosphamide metabolism who were not receiving other drugs known to affect drug metabolism were selected 9 were taking fluconazole and 13 were controls. The plasma clearance was significantly lower in patients taking concomitant fluconazole (2.4 versus 4.2 1/ hour/m ). It is unclear whether this interaction is associated with a reduction in the therapeutic efficacy of cyclophosphamide. 

Of particular significance to toxicology is that a chemical with a mechanism of action that requires interaction with an active metabohc process may only exert toxicity when hair growth is in an active growth phase. Exposure at other times may not elicit any response. Many cytotoxic chemicals (e.g., cancCT chemotherapeutic drugs and immunosuppressants such as cyclophosphamide) with a mechanism of action that is to kill dividing cells will produce hair loss (alopecia) as an imwanted side effect of nonselective activity. 

Some specificity has been achieved in the case of the anti-tumor drug cyclophosphamide. This drug takes advantage of the fact in the cancer patient there will be a greater dephosphorylating (loss of phosphate) activity in the cancer cells than in the normal cells, and hence it will interact to a greater extent with the former. 

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