Intermittent, alternating, and concurrent regimens of zidovudine and 2'-3' dideoxycytidine in the LP-BM5 murine induced immunodeficiency model.

The murine retrovirus-induced immunodeficiency model, LP-BM5, was used to evaluate the efficacy of intermittent and alternating regimens of zidovudine (azido-2'-3'dideoxythymidine; AZT) and 2'-3' dideoxycytidine (ddC) compared with continuous and concurrent therapy. Intermittent oral AZT therapy was less effective in protecting mice inoculated with LP-BM5 virus than was continuous oral AZT therapy. Continuous oral ddC therapy (80 mg/kg/day) increased survival time an average of 3.5 weeks (P less than .001) compared with that in untreated LP-BM5-infected mice. Alternating weekly AZT and ddC therapy, which increased survival time 3.5 weeks (P less than .001), was more effective than either therapy administered intermittently, although not additive or synergistic. Concurrent AZT and ddC therapy was no more effective than continuous AZT therapy alone in this model, with a 4.4-week increase in survival time (P less than .001).