OBJECTIVES: The National Health Service in England (NHS England) does not 
provide pre-exposure prophylaxis (PrEP) against HIV, forcing people to purchase 
generic versions on the internet. However, there are concerns about the 
authenticity of medicines purchased online. We established an innovative service 
offering plasma tenofovir (TFV) and emcitrabine (FTC) therapeutic drug 
monitoring for people buying generic PrEP online, to ensure that drug 
concentrations in vivo were consistent with those of propriety brands and 
previously published data.
METHODS: TFV/FTC concentrations were measured by ultra-performance liquid 
chromatography ultraviolet detection. Evaluation of renal function and testing 
for HIV, hepatitis B virus (HBV) and hepatitis C virus (HCV) were also carried 
out, at baseline and every 3-6 months, with risk reduction advice.
RESULTS: A total of 293 individuals presented having purchased PrEP on the 
internet: 85% were white, 84% were taking daily PrEP, and 16% were event-driven. 
Most were on generic TFV disoproxil fumarate (TDF)/FTC from Cipla Ltd. Median 
(range) TFV and FTC plasma concentrations were 104 (21-597) ng/mL and 140 
(17-1876) ng/mL, respectively. All concentrations were above our established 
plasma TFV and FTC targets, based on previously published data. Renal function 
was normal in all evaluable individuals and no new cases of HIV, HBV or HCV 
infection were seen.
CONCLUSIONS: In a population at high risk of HIV acquisition, who cannot yet 
access PrEP on the NHS, concentrations of TFV and FTC in generic formulations 
purchased over the internet were similar to (or slightly higher than) those 
measured in phase I studies with the original formulation from Gilead 
(Truvada™), which has demonstrated high levels of protection against HIV 
infection in previous PrEP clinical trials.