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B-QuiCK: HIV pre-exposure prophylaxis (PrEP)

Pre-exposure prophylaxis (PrEP):

  • PrEP is an oral combination medicine (tenofovir disoproxil 245 mg with emtricitabine 200 mg) available fully funded with Special Authority approval for patients considered at higher risk of HIV exposure
    • Suitability criteria developed to aid assessment of HIV exposure risk are available here
  • PrEP can be by prescribed any relevant practitioner, including general practitioners and nurse practitioners

Testing before initiating PrEP

  • Baseline HIV status
    • Repeat in one month if high-risk exposure within 45 days of baseline test
    • Consider PEP if the high-risk exposure occurred within 72 hours
  • Blood tests for syphilis and hepatitis B* and C (unless known immunity); hepatitis A* test is also recommended, but not funded
  • NAAT for chlamydia and gonorrhoea (first-pass urine for males, and rectal, urethral, vaginal and pharyngeal swabs as indicated)
  • eGFR, creatinine, protein:creatinine ratio
  • Liver function tests
  • Pregnancy testing in people of childbearing potential

* Offer vaccination if not immune, however, neither hepatitis A nor B vaccination is funded in this situation

PrEP can be prescribed two ways

  • Daily PrEP is recommended for all patients who are at higher risk of HIV infection
  • Initially prescribe a quantity of PrEP sufficient for 90 days
  • Event-driven PrEP is only recommended for cisgender males and people assigned male at birth who are not taking oestrogen-based gender affirming hormone therapy if daily PrEP is not practical or acceptable
  • Event-driven PrEP should not be offered to:
    • People assigned female at birth or people taking oestrogen-based gender affirming hormone therapy
    • People with chronic hepatitis B (possibility of hepatitis flares after event-driven treatment stops)

Prescribing considerations based on patient history or baseline test results

  • Do not initiate PrEP in patients with an indeterminate HIV test; assess for symptoms and signs of acute HIV infection and discuss with an infectious diseases or sexual health physician
    • PrEP should only be commenced once HIV infection has been ruled out
  • Discuss patients with chronic hepatitis with a hepatologist or infectious diseases physician before initiating PrEP
    • PrEP should be prescribed daily (and not event-driven) for patients with hepatitis B; discuss the importance of adherence
  • Do not delay PrEP initiation in people with a bacterial STI
  • PrEP is contraindicated in people with an eGFR < 60 mL/min/1.73 m2
  • Offer contraception to all people of child-bearing potential taking PrEP who do not wish to become pregnant
  • PrEP may be suitable for people aged <18 years, but this is an unapproved indication and should be discussed with a sexual health or infectious diseases physician

Follow-up and monitoring

  • Follow-up every three months is recommended for all patients taking PrEP; discuss adverse effects and adherence
  • Recommended laboratory testing (available here) should occur within two weeks prior to prescription renewal
  • Advise that if a dose is missed, it can be started again when remembered (a double dose should not be taken)

PrEP adverse effects are generally mild and transient

  • Gastrointestinal symptoms, e.g. nausea, vomiting, abdominal pain, flatulence, diarrhoea, and headache, are commonly reported in the first month of use; they are unlikely to persist beyond three months
  • The principal concerns are acute kidney injury and hepatic impairment (increased risk of hepatic adverse effects in patients with chronic hepatitis)
    • Advise patients to seek immediate medical attention if they have symptoms of concern outside of their scheduled follow-up appointments
  • Monitor for acute HIV infection (due to non-adherence to the regimen or pre-existing infection)
  • Bone density may be reduced slightly in people taking PrEP; advise older patients or those with multiple risk factors for fractures on strategies to maintain bone density, e.g. adequate dietary calcium intake and exposure to sunlight, regular weight-bearing exercises, reducing alcohol intake, smoking cessation

Managing declining renal function

  • If eGFR drops to < 60 mL/min/1.73 m2 while taking PrEP, discuss with a sexual health or infectious diseases physician with expertise in PrEP, or a nephrologist, as continuation may be possible
    • Event-driven PrEP may be a practical option for eligible patients with an eGFR close to the threshold
  • Concurrent use of medicines that are nephrotoxic or compete for active tubular secretion may cause serum levels to increase, e.g. valaciclovir, aminoglycosides or long-term NSAIDs
  • Nephrotoxicity is rare in patients taking PrEP, although proximal tubular dysfunction can occur

Withdrawing PrEP

  • Withdraw PrEP if no longer at higher risk of HIV (e.g. enter a mutually monogamous relationship), or if adherence is not adequate, i.e. fewer than four doses per week for people prescribed daily PrEP
  • PrEP should be continued after the last potential HIV exposure for at least:
    • Two days in cisgender males and people assigned male at birth who are not taking oestrogen-based gender affirming hormone therapy, i.e. one dose 24 hours after the last exposure and another dose 48 hours afterwards for both daily and event-driven regimens
    • Seven days in all other patients
  • Discuss patient with chronic hepatitis B infection with a hepatologist or infectious diseases physician before withdrawing from PrEP (risk of hepatitis reactivation)

Continue to promote the consistent and correct use of condoms to prevent HIV and other STIs

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