Clinical Cases in Pharmacology Clinical Cases  ·  Infectious Disease II  ·  HIV  ·  Long-Acting CAB PrEP vs. Oral PrEP
Infectious Disease II, Case 0006 — HIV

PrEP That Doesn't Depend on Remembering

His oral PrEP keeps lapsing for the same reason most people's does — daily life gets in the way — and an injection every two months promises to remove that problem. It also introduces a different one, further out, that daily pills never carried.

Abbreviations, terms, and other agents mentioned in this case PrEP — pre-exposure prophylaxis  ·  HIV — human immunodeficiency virus  ·  PK — pharmacokinetic  ·  MSM — men who have sex with men
Presentation

J.P., a 24-year-old man, works as a line cook at a restaurant with an unpredictable schedule — some weeks closing shift after closing shift, other weeks a run of early prep shifts that start before sunrise — and started daily oral PrEP eighteen months ago after a conversation with a friend who'd been on it for years. He's genuinely motivated; he just keeps forgetting doses during the weeks his schedule flips, and pharmacy refill data shows two gaps of over two weeks each in the past year, both of which lined up with a stretch of overnight shifts by his own recollection. He has no chronic illness, takes no other medications, and his most recent HIV test, drawn today as part of his routine quarterly visit, is negative.

He's asking today about switching to injectable cabotegravir after seeing another patient in the waiting room get one. HPTN 083, the trial that tested exactly this switch's rationale, randomized cisgender men and transgender women who have sex with men to injectable cabotegravir against daily oral tenofovir/emtricitabine and found injectable cabotegravir the more effective option overall, a result driven substantially by the fact that an injection every two months doesn't depend on remembering something every single day. But the same trial's own breakthrough infections raised a distinct concern: a small number of participants who acquired HIV during the drug's long pharmacokinetic tail — the months of slowly falling, sub-therapeutic drug levels after an injection is stopped or delayed — showed integrase-class resistance mutations, a failure mode daily oral PrEP, which clears the body within days of stopping, doesn't carry in the same way. His own exposure pattern is ongoing rather than episodic, which is exactly the profile the trial's superiority result was strongest for — the adherence gap that matters most isn't a single missed weekend, it's the kind of multi-week lapse his refill history already shows twice over.

J.P. · 24 Quarterly Visit
Current regimen
Daily oral tenofovir DF / emtricitabine
Adherence history
Two gaps >2 weeks in the past 12 months (pharmacy refill data)
Today's HIV test
Negative
Renal function
Creatinine 0.9 mg/dL, normal
Exposure pattern
Ongoing, variable-frequency
Other history
No chronic illness, no other medications

PrEP clinic, quarterly follow-up

Infectious Disease / HIV Physician Opening

HPTN 083 tested exactly the switch he's asking about — injectable cabotegravir against daily oral PrEP in men who have sex with men — and found injectable cabotegravir superior overall, largely because it removes the daily-memory dependency that's the documented reason his own protection has lapsed twice in the past year. I'd support the switch.

Clinical Pharmacologist Response

The efficacy comparison is real and I'm not arguing against it in general.

But injectable cabotegravir has a failure mode oral PrEP doesn't: HPTN 083's own breakthrough infections, when they occurred during the drug's long pharmacokinetic tail — months of declining, sub-therapeutic levels after a delayed or missed injection — showed integrase-class resistance in a way daily pills, which clear the body within days of stopping, simply don't produce. Committing him to an injection schedule still requires him to show up reliably; it doesn't eliminate the adherence variable, it just changes what a missed appointment costs. There's also a harder line here, not a soft consideration — the label carries a boxed warning specifically because cabotegravir given during undiagnosed acute infection has produced integrase-resistant virus. His test today is negative, but given an ongoing exposure pattern, I want that confirmed as close to the injection as our workflow allows, not treated as settled by a screen drawn this morning.

PrEP Clinic Nurse Practitioner Final

Both of those points are about which product handles a lapse better. Neither addresses why his lapses actually happened — his schedule flips unpredictably between early and late shifts, and a fixed-time daily pill doesn't survive that kind of week. An injection every two months is genuinely easier to plan around than a daily pill is, for exactly his kind of schedule. I'd support the switch too, but I want a concrete injection-day reminder system built into his chart before his first dose, so we're not assuming the switch alone fixes what a pill bottle never could.

Regimen selected
Cabotegravir (Long-Acting Injectable)
INSTI · Every 2 months after oral lead-in
Selected given his documented adherence gaps on daily oral PrEP and HPTN 083's superiority result for this exact population.
Oral Cabotegravir Lead-In (4 Weeks)
INSTI · Tolerability check before first injection
Standard practice before the first injection, to confirm tolerability while still on an easily-discontinued oral formulation.
Daily Oral Tenofovir DF / Emtricitabine — Discontinued
NRTI-Based PrEP · Prior regimen
Discontinued in favor of the injectable option; his own refill history shows this schedule hasn't reliably protected him.
Quarterly HIV Testing (Intensified)
Monitoring · Every visit, indefinitely
Maintained at standard PrEP-monitoring frequency specifically to catch any breakthrough infection early, given the resistance concern raised in the debate.
Where this was left

Agreed: switch to injectable cabotegravir after a 4-week oral lead-in, with a structured injection-day reminder system added to his chart per the nurse practitioner's condition. Quarterly HIV testing continues at standard PrEP intervals specifically to catch any breakthrough infection during the drug's pharmacokinetic tail as early as possible, addressing the pharmacologist's concern through monitoring rather than through declining the switch.

Educational content only — a composite teaching case, not a real patient encounter or a substitute for clinical guidance. About These Cases →