Intolerable side-effects result in many clients failing to complete the prescribed course of NPEP. In a meta-analysis of PEP adherence, completion rates were 57% overall and 67% in MSM.^[15] Toxicity driven discontinuation was commoner with three-drug regimens than with two-drug regimens (2% vs 9% respectively).^[16] The World Health Organization (WHO) recommends that three antiretroviral drugs be universally used^[17].

Given that between one half and one third of clients do not complete the prescribed course principally because of side-effects, the choice of safe, tolerable drugs for use in NPEP is paramount and nurses have an important role in supporting clients on PEP who experience side-effects (see Table 12). In Australia, Truvada (emtricitabine and tenofovir disoproxil fumarate) with the integrase inhibitor raltegravir is widely used as three-drug NPEP. In men who have sex with men, it has been shown to be well tolerated with high rates of on-drug adherence, treatment completion and, were a protease inhibitor the third drug, a low risk of potentially dangerous drug reactions.^[18] More recently, Truvada with the non-nucleoside reverse transcriptase inhibitor (NNRTI) rilpivirine and Truvada with the integrase inhibitor dolutegravir have both been evaluated as three-drug HIV postexposure prophylaxis in men who have sex with men; both have also demonstrated low toxicity, high adherence, high completion rates and the added convenience of once-daily dosing.^[19] [20]