Some sexual and injecting drug use exposures are similarly risky. It has been demonstrated that combination therapies can lower the amount of HIV in the blood, sometimes to undetectable levels. The impact of the new treatments on HIV levels in semen, and therefore on sexual transmission, is still unknown. Although it may be less likely, it is still possible that HIV could be transmitted by someone using the new drugs. If so, the strain of HIV transmitted is more likely to be drug-resistant.
Protease inhibitors are complicated to use correctly.
For example, some new drugs require refrigeration, which is nearly impossible for someone living in a shelter or temporary housing. Patients on protease inhibitors commonly take more than two dozen pills daily. If the drugs are not used correctly and consistently, strains of HIV that are resistant to the current drugs could emerge. Even in the short term, some people do not improve. While some protease inhibitors have been shown to interact with common prescription medicines, there may be additional, as yet undiscovered, interactions of importance.