Cobicistat

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What it isPotent CYP3A inhibitor without antiviral activity; pharmacokinetic booster in HIV regimens.

Why this oneUnlike ritonavir, it was engineered solely as a booster, simplifying fixed-dose antiretroviral combinations.

What limits itEvery co-prescription needs interaction review. It raises creatinine by blocking tubular secretion without reducing true filtration.

FDA-approved for

pharmacokinetic booster (HIV) (2014)

FDA label

Read the full label on DailyMed ↗

FDA dosing	Population	Start	Target
HIV-1: PK booster of atazanavir (with other antiretrovirals)	Adults & peds >=35 kg	150 mg QD with food, at same time as atazanavir 300 mg QD	150 mg QD
HIV-1: PK booster of atazanavir	Peds 14 to <25 kg (with atazanavir 200 mg QD)	90 mg QD with food	90 mg QD
HIV-1: PK booster of atazanavir	Peds 25 to <35 kg (with atazanavir 200 mg QD)	150 mg QD with food	150 mg QD
HIV-1: PK booster of darunavir (no darunavir resistance substitutions)	Adults & peds >=40 kg	150 mg QD with food, at same time as darunavir 800 mg QD	150 mg QD
HIV-1: PK booster of darunavir	Peds 15 to <25 kg (darunavir 600 mg): 90 mg; 25 to <30 kg (darunavir 600 mg): 150 mg; 30 to <40 kg (darunavir 675 mg): 150 mg	90-150 mg QD with food per weight band	Per weight band

Renal No adjustment needed (incl. severe impairment); however with tenofovir DF not recommended if estimated CrCl <70 mL/min; cobicistat lowers estimated CrCl without affecting true glomerular function

Hepatic Mild-moderate: no adjustment; severe: no data

Not an antiretroviral itself - CYP3A inhibitor used only to boost atazanavir or darunavir

Instructions

Must be coadministered at the same time as atazanavir or darunavir, with food, plus other antiretrovirals
Assess estimated CrCl before initiation; with tenofovir DF also urine glucose and protein at baseline (serum phosphorus if CKD)
Not interchangeable with ritonavir for darunavir 600 mg BID, fosamprenavir, saquinavir, or tipranavir
Do not use with regimens containing ritonavir or other cobicistat-containing products, or with more than one agent requiring PK enhancement

Contraindications

Coadministration (with atazanavir or darunavir) with drugs whose altered levels cause serious/life-threatening events or loss of effect: alfuzosin, ranolazine, dronedarone, carbamazepine, phenobarbital, phenytoin, colchicine, rifampin, irinotecan (atazanavir only), lurasidone, pimozide, ergot derivatives (dihydroergotamine, ergotamine, methylergonovine), St. John's wort, drospirenone/ethinyl estradiol, lomitapide, lovastatin, simvastatin, nevirapine, sildenafil for PAH (Revatio), indinavir, triazolam, oral midazolam

Cautions

Decreases estimated CrCl without affecting true GFR - assess CrCl at baseline; confirmed serum creatinine rise >0.4 mg/dL warrants close renal monitoring
New-onset/worsening renal impairment incl. acute renal failure and Fanconi syndrome when used with tenofovir DF - monitor CrCl, urine glucose/protein; avoid with nephrotoxic agents
Serious interactions via CYP3A inhibition - review all comedications before and during therapy
Not recommended: with more than one PK-enhanced antiretroviral, protease inhibitors other than once-daily atazanavir or darunavir, ritonavir-containing regimens, darunavir+efavirenz/nevirapine/etravirine, atazanavir+etravirine

Adverse reactions

With atazanavir: jaundice (6%)
Rash (5%)

Pregnancy Not recommended during pregnancy (with darunavir or atazanavir) - substantially lower exposures in 2nd/3rd trimesters; do not initiate in pregnancy and switch to alternative regimen if pregnancy occurs; exposure registry available

Lactation No human milk data (present in rat milk); breastfeeding risks: HIV-1 transmission, viral resistance in HIV-positive infants, infant adverse reactions

NO BOXED WARNINGS

Principal riskEvery co-prescription must be checked for CYP3A4

Cost, est. cash$300–$2,500/month

Generic entry2024

Classes and tags

Clinical profile

Therapeutic safety burden1 / 4

Overdose danger1 / 4

Weight-gain liability0 / 4

Sedation liability0 / 4

QT / Torsades0 / 4

Direct muscarinic antagonism0 / 4

Embryofetal risk1 / 4

Legacy pregnancy categoryUnknown / historical label unavailable

Defining liabilityGenerally tolerated at therapeutic doses; clinically important risks are agent-specific and increase with interactions or organ impairment.