HIV post-exposure prophylaxis (PEP) in Singapore.

HIV PEP (post-exposure prophylaxis) is a short course of antiretroviral medication taken after a specific HIV exposure to prevent the virus from establishing infection. It's the emergency, time-limited counterpart to HIV PrEP (which is taken before exposure on an ongoing basis).

The 72-hour window. PEP must be started within 72 hours of exposure to be effective. The biological reason: HIV needs time to establish infection in the body's cells, and antiretroviral medication can interrupt this process if present in adequate concentration. After approximately 72 hours, the medication is significantly less likely to prevent established infection.

Within that 72-hour window, earlier is dramatically better:

• Within 1-2 hours of exposure: maximum effectiveness
• Within 24 hours: still highly effective
• 24-48 hours: effective, with reduced margin
• 48-72 hours: borderline - start only if the exposure is genuinely high-risk
• Beyond 72 hours: PEP is not started; the structured testing pathway is used instead

Effectiveness. Studies estimate PEP reduces HIV transmission risk by approximately 80% when started promptly and taken as prescribed.¹ The 28-day course must be completed - stopping early significantly reduces effectiveness.

When PEP is appropriate. PEP is for specific, identifiable exposures with meaningful HIV transmission risk: unprotected sexual contact (vaginal, anal, or oral) with a partner of unknown or positive HIV status; sharing of injection equipment; occupational needlestick injury involving HIV-positive or unknown-status source; sexual assault - PEP is offered routinely as part of post-assault care.

When PEP is not appropriate. Exposure clearly more than 72 hours ago (use the structured testing pathway instead); exposure with negligible risk (e.g. kissing, sexual contact with a partner on effective HIV treatment with confirmed undetectable viral load - U=U eliminates transmission); ongoing pattern of high-risk activity rather than a single exposure (consider HIV PrEP instead).

What happens during a PEP consultation. The consultation is fast - typically 30-45 minutes including history, baseline blood draw, and medication initiation. Treatment can start during the consultation. The structured follow-up - testing at 4-6 weeks, 12 weeks, and 12 weeks - is scheduled at the same visit.

The medications. PEP is either a 2-drug or a 3-drug combination, selected according to the assessed risk of the exposure. The 2-drug regimen is taken once daily. The 3-drug regimen is available in once-daily and twice-daily forms, depending on the combination prescribed. These are the same classes of antiretroviral medication used in HIV PrEP.

Together this provides robust antiretroviral coverage. The specific regimen may be adjusted based on individual medical history, kidney function, or potential drug interactions.

Duration: 28 days, no breaks. PEP must be taken every day for the full 28 days. Missed doses reduce effectiveness. The biggest cause of PEP failure isn't the medication - it's incomplete courses.

Side effects. PEP is generally well-tolerated for the short 28-day duration. Common, mild, and usually transient: nausea, mild gastrointestinal upset (first 1-2 weeks especially), fatigue, headache, sleep disturbance. Less common: mood changes, kidney function changes (monitored), liver function changes. If side effects significantly affect adherence, your clinician will discuss management - including possible regimen switches.

Baseline workup before starting. PEP is initiated at the consultation, often immediately. The baseline workup typically includes a 4th-generation HIV testing to confirm pre-exposure HIV-negative status; syphilis serology, chlamydia and gonorrhoea PCR, hepatitis B and C - see STD testing; kidney function (creatinine, eGFR) - PEP medications are kidney-cleared; liver function - baseline for monitoring during the course; pregnancy test if applicable.

If any baseline test is positive, treatment is coordinated alongside PEP. For example, if syphilis or chlamydia is detected at baseline, STD treatment is initiated at the same time as PEP.

Follow-up testing schedule:

The 12-week test is the definitive endpoint for most patients. Negative testing at 12 weeks after exposure (or after completing PEP, whichever is later) is conventionally considered fully reassuring.

Co-ordination with ongoing prevention. If your situation suggests ongoing HIV exposure risk beyond this single event, HIV PrEP should be discussed. Transition from PEP to PrEP at the end of the 28-day course is straightforward and provides continuous protection. Message your personal concierge if you'd like to plan ahead.

Before your visit. For urgent PEP consultations, the priority is getting you in the door - paperwork is minimal at first. WhatsApp or call the clinic; we coordinate same-day where possible. Bring identification.

If you've had a specific exposure, try to recall basic details about the timing, type of contact, and partner status if known. We don't need detailed history before the consultation - that conversation happens with the clinician.

During your visit. The PEP consultation lasts approximately 30-45 minutes. Our medical team conducts focused risk assessment - when, what, with whom (status if known), any other concurrent risk factors. The conversation is matter-of-fact and respectful; the goal is accurate risk stratification.

Baseline blood draw includes 4th-generation HIV testing, syphilis serology, hepatitis B and C, kidney function, and liver function. A pregnancy test is included for women of childbearing potential. Urine sample for chlamydia and gonorrhoea PCR. Throat or rectal swabs if exposure history warrants.

If PEP is appropriate, the first dose can be taken at the consultation. You leave with the full 28-day supply and a follow-up schedule already booked.

After your visit. Your personal health concierge contacts you within 1-2 days to check side effect tolerability and answer any questions. The follow-up tests at week 4-6 and 12 are scheduled in advance.

If baseline tests reveal a concurrent STI, treatment is coordinated within the same day. If baseline HIV testing returns positive (rare but possible - pre-existing infection that PEP wouldn't have caught), specialist HIV care referral is activated immediately, with continuity through your personal health concierge.

Confidentiality. Records are encrypted. Hisential does not share information with employers, family members, occupational health teams, or insurers without your explicit consent. For occupational exposures, you choose whether and how to report.