Because immunosuppressed HIV-infected patients must take many medications for the management of acquired immunodeficiency syndrome (AIDS)-associated diseases in addition to antiretroviral therapy, intermittent regimens for the prophylaxis of opportunistic infections such as Pneumocystis carinii pneumonia and toxoplasmosis may help to improve quality of life and may prolong survival.

Several intermittent regimens, however, have proven insufficient to adequately prevent opportunistic infections [1-4]. In addition, because compliance in these patients is a matter of concern, regimens with a "safety margin" sufficient to retain their effectiveness despite irregular compliance are preferable.

We agree with Zamora and colleagues that intermittent low-dose regimens may be useful for primary prophylaxis of P. carinii pneumonia and toxoplasmosis. In Zamora and colleagues' study, however, 4 of 157 patients presented with P. carinii pneumonia and 6 of 157 presented with toxoplasmosis, despite trimethoprim-sulfamethoxazole prophylaxis. In our study, none of 104 patients and only 1 of 65 T. gondii-seropositive patients receiving trimethoprim-sulfamethoxazole developed pneumonia or toxoplasmosis, respectively [5]. Although comparison among trials is difficult and differences in events are small, available data suggest that the efficacy of the trimethoprim-sulfamethoxazole regimen used by Zamora and associates may not be identical to that of our regimen because trimethoprim-sulfamethoxazole may not prevent P. carinii pneumonia and toxoplasmosis in some cases. On the other hand, the proper method for evaluating the effectiveness of different regimens is a randomized clinical trial.

Regarding the regimen of dapsone plus pyrimethamine, only one patient in our study who received this regimen presented with P. carinii pneumonia [5]. If the eight patients in Zamora and colleagues' study who developed an episode of P. carinii pneumonia had good compliance, we could conclude that the dapsone-pyrimethamine regimen used by Zamora and colleagues is insufficiently effective to be recommended for the simultaneous primary prophylaxis of P. carinii pneumonia and toxoplasmosis.

Finally, probably the most important issue in managing immunosuppressed, HIV-infected patients who must receive long-term primary or secondary prophylaxis for opportunistic infections is assuring the best possible compliance and a good physician-patient relationship.