HIV — PrEP (Pre-Exposure Prophylaxis)

Daily & on-demand dosing, eligibility & monitoring

Field: Infectious DiseasesCode: ID-05AUpdated: June 2026Reference: ASHM National PrEP Guidelines (Jul 2025)

PrEP is highly effective when taken as prescribed. Daily dosing needs a 7-day lead-in before full protection and suits anyone at ongoing risk; on-demand (2-1-1) dosing is an event-driven option for a defined eligible group. Confirm renal function and HIV-negative status before every script.

Dosing options (eGFR over 60 needed)

Daily: TDF/FTC (or TAF/FTC — Descovy, now PBS-listed for daily use) once daily, continuous. Full protection needs a 7-day lead-in before condomless exposure.
On-demand (2-1-1): TDF/FTC only — not Descovy. 2 tablets 2–24h before sex; 1 tablet 24h after the first dose; 1 more tablet 24h after that.
Stopping daily: continue for 7 days after the last potential exposure, then stop.
Stopping on-demand: 2 further tablets after the last sex act — one at 24h, one at 48h.

Restarting on-demand dosing. If sex resumes within 7 days of the last tablet, a single loading tablet restarts protection. If it has been more than 7 days, the full 2-tablet loading dose is needed again.

Who is eligible

HIV-negative with ongoing risk — condomless anal/vaginal sex with partners of unknown or HIV-positive status, shared injecting equipment, or a partner not yet virally suppressed.
On-demand dosing specifically: assigned male sex at birth, not using exogenous oestradiol-based hormones, no chronic HBV needing treatment or with cirrhosis, and eGFR over 60 (caution 30–60).
Acute seroconversion illness (fever, rash, lymphadenopathy) must be excluded before starting — starting PrEP during undiagnosed acute HIV risks drug resistance.

Monitoring on PrEP

Baseline: HIV Ag/Ab, renal function, HBV/HCV serology, STI screen and pregnancy test if relevant. 3-monthly: HIV test and STI screen; renal function at 3 months then 6-monthly. Annually: comprehensive review of risk, adherence and ongoing need.

Safety

Never start or continue PrEP during a suspected acute HIV seroconversion illness — test first.
eGFR under 60 is a contraindication to TDF-based PrEP; review TAF-based options or refer.
Stopping PrEP in a patient with chronic HBV can trigger a hepatitis flare — check HBV status first.

Red flags / refer

Suspected acute seroconversion illness, or a positive/indeterminate HIV test on PrEP.
eGFR 30–60, declining renal function, or chronic HBV needing treatment.
Eligibility for on-demand dosing is unclear (e.g. feminising hormone use) — discuss daily dosing instead.

ID-05A v1.0 · Reviewed Jun 2026 · Review Jun 2027

Companion sheet: ID-05B (PEP). See also ID-01/02 (diagnosis & ART) and ID-03 (STI screening). Verify against the ASHM National PrEP Guidelines (updated Jul 2025) at ashm.org.au and current PBS listing at pbs.gov.au.