Managing drug interactions

Limited information is available on the HIV Drug Interactions website run by the Liverpool HIV Pharmacology Group. They provide information on potential interactions between protease inhibitors (PIs) and non-nucleoside reverse transcriptase inhibitors (NNRTIs) and five anti-cancer drugs: cyclophosphamide, doxorubicin (Adriamycin), paclitaxel (Taxol), vinblastine (Velbe), and vincristine (Oncovin). This advises that doxorubicin does not interact with anti-HIV drugs (whereas the other agents do), and that nevirapine presents fewer problems than other antiretrovirals.

Drugs from the nucleoside analogue reverse transcriptase inhibitor (NRTI) class do not present the same type of drug interaction issues associated with PIs and NNRTIs as they use different routes to pass through the body. However, their use in combination with chemotherapy may still be problematic because of overlapping side effect profiles. AZT (zidovudine, Retrovir) plus chemotherapy increases the risk of bone marrow suppression and so is generally not used in this setting. 3TC (lamivudine, Epivir), d4T (stavudine, Zerit) and ddI present fewer problems. There appears to be little information on the use of abacavir (Ziagen) with chemotherapy. It may be a concern that symptoms of the hypersensitivity reaction associated with this drug may be difficult to distinguish from the systemic side effects seen during chemotherapy.

Given that the daily pill burden may be quite high, taking liquid formulations of anti-HIV medications may be preferable for some people. In addition, chemotherapy can cause mucositis, an inflammation of the mucous membranes which may cause difficulty swallowing.