Educational draft · awaiting clinical reviewUse Rapid for revision, not patient-care decisions. Check current national and local guidance and the BNF or BNFC before acting.
2 min synopsisUK scopeSources checked 13 Sept 2026Clinical review pending
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Possible HIV infection while taking PrEP
A reactive result, detectable RNA, acute retroviral syndrome, or repeated exposure during poor adherence may represent breakthrough HIV and creates a risk of resistance on two-drug prophylaxis.
Action: Stop treating the situation as routine prevention, obtain urgent antigen-antibody and HIV RNA testing, and involve an HIV specialist to establish a complete treatment regimen without a poorly planned drug gap.
Synopsis
Offer HIV PrEP through an equitable risk conversation, exclude acute infection, select daily or event-based dosing by exposure anatomy, and monitor renal, hepatitis and STI health.
PrEP is for HIV-negative people who may benefit from protection before future sexual or injecting exposure; eligibility should be individualised and equitable.
Confirm a laboratory HIV-negative result and use HIV RNA when acute symptoms, very recent risk or recent PEP or PrEP makes serology uncertain.
Check renal function, hepatitis B status, pregnancy, medicines and site-specific STIs before oral tenofovir disoproxil with emtricitabine.
Key red flags
Fever, rash, pharyngitis, lymphadenopathy or diarrhoea after recent exposure requires HIV RNA assessment before starting or renewing oral PrEP.
A reactive or discordant HIV result must not be managed by continuing two-drug prophylaxis as if infection were excluded.
Chronic hepatitis B makes intermittent dosing and stopping tenofovir-emtricitabine clinically consequential because HBV rebound can cause hepatitis.
Reduced renal function, proteinuria or concurrent nephrotoxic medicine requires regimen and monitoring review before oral tenofovir disoproxil.
Pregnancy, breastfeeding and gender-affirming hormones require inclusive specialist discussion but are not automatic reasons to deny effective prevention.
Possible acute HIV
Fever, rash, sore throat, nodes or diarrhoea after recent risk requires urgent RNA testing.
Breakthrough concern
New reactivity or detectable RNA during PrEP requires immediate specialist treatment assessment.
HBV-associated stopping risk
Chronic hepatitis B can rebound when tenofovir-emtricitabine is interrupted or stopped.
Investigation priorities
01
Laboratory fourth-generation HIV testFirst step
Exclude established infection before starting and at least every three months during PrEP.
Management branches
Worked caseQuick-start before anticipated exposure
An HIV-negative adult expects receptive vaginal sex tomorrow and requests oral PrEP today.
Exclude acute symptoms, send a laboratory HIV test, check renal and hepatitis B status, pregnancy and current medicines.
Take two tenofovir-emtricitabine tablets 2 to 24 hours before risk when clinically eligible.
Daily dosingProtect unpredictable or frequent exposure
Exposure is frequent, may occur without notice or the user prefers a simple routine.
Key medicines
Daily oral PrEPGive tenofovir disoproxil 245 mg and emtricitabine 200 mg as one tablet orally once daily after HIV-negative status is established.Monitor HIV and renal function, assess hepatitis B before stopping and investigate acute-HIV symptoms immediately to prevent resistance.
Quick-start event-based oral PrEPTake two tenofovir and emtricitabine tablets 2 to 24 hours before risk; continue one daily for two days after the last anal or insertive-sex risk, or for seven days after receptive vaginal, neovaginal or injecting risk.Not a substitute for three-drug PEP after an unprotected past exposure; extend the daily tail if exposure continues and obtain specialist advice before intermittent use with chronic hepatitis B.
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 13 Sept 2026; clinical approval remains outstanding.