PrEP Prescription Lengths: Associations with Patient Retention, On-Time Renewal and Demographics.

PrEP prescription length patterns have not been well-studied. We examined PrEP prescribing at a large medical center in New York City, to explore (1) variation in prescription lengths at initiation and return, overall and by patient demographics, (2) associations between prescription length and subsequent retention and continuity, and (3) associations between prescription length and HIV testing. We analyzed electronic medical record data for 11,072 PrEP prescriptions among 1,968 patients, between 2015 and 2022. Prescription length was defined as the total days of pill supply in a prescription, including all refills. Retention was defined as the total number of PrEP prescriptions each patient received. Continuity was defined as receiving a prescription renewal before running out of pills, assuming daily dosing. We found that PrEP prescription lengths were variable and inconsistent. The majority of patients received a 30-day initial prescription, but those patients were more likely to experience a gap in PrEP coverage before their second prescription. Overall, longer prescriptions were associated with greater retention (i.e., higher total count of return prescriptions) and greater continuity (i.e., higher percentage of on-time renewals). We also found that longer returning prescriptions were less likely to be given to Black and Hispanic patients, and shorter prescriptions were associated with HIV testing within 3-months of PrEP start. Findings suggest that prescription length has critical implications for PrEP retention and continuity, with longer prescriptions promoting greater retention and fewer coverage gaps. Providers should consider the impact of prescribing practices on patient experience, engagement in care, and PrEP effectiveness.