Condom-use decision making in the context of hypothetical pre-exposure prophylaxis efficacy among substance-using men who have sex with men: Project MIX.

OBJECTIVE: To examine condom-use decision making in the context of hypothetical pre-exposure prophylaxsis (PrEP) efficacy among men who have sex with men who use alcohol and other substances during sex.
METHODS: Substance-using men who have sex with men were recruited in 4 US cities for a behavioral intervention trial. Three groups were defined as follows: men who indicated that to not use a condom for receptive/insertive unprotected anal intercourse (UAI) while using PrEP, PrEP would need to be: (1) "almost always or always" effective (high efficacy); (2) effective "at least half the time or more but not almost always or always" (mid-range efficacy corresponding to recent PrEP trial results); (3) effective "less than half the time" (low efficacy). The mid-range efficacy group was compared with the low-efficacy group (as the reference) and to the-high efficacy group (as the reference).
RESULTS: Among 630 men who never used PrEP, 15.2% were in the mid-range efficacy group for receptive UAI and 34.1% in the mid-range efficacy group for insertive UAI. Scores on difficulty communicating about safer sex while high were significantly higher in the mid-range efficacy group compared with each of the other groups for both receptive and insertive UAI. Men who seemed to be differentiating PrEP use by anal sex role also scored higher on communication difficulties, although scoring lower on condom intentions.
CONCLUSIONS: Communication about safer sex while under the influence of alcohol or other substances and condom intentions are important factors to consider for HIV prevention interventions for PrEP users.