Guidelines for the Use of Antiretroviral Agents in Pediatric HIV Infection

Pharmacokinetic Enhancers

Cobicistat

Drug Interactions

Additional information about drug interactions is available in the Adult and Adolescent Antiretroviral Guidelines and the HIV Drug Interaction Checker.

• Metabolism: Metabolism of cobicistat (COBI) is mainly via cytochrome P450 (CYP) 3A4 and, to a lesser degree, CYP2D6. COBI is a strong inhibitor of CYP3A4 and a weak inhibitor of CYP2D6. COBI also inhibits breast cancer resistance protein, P-glycoprotein (P-gp), the organic anion transporting polypeptides organic anion transporting polypeptide (OATP) 1B1 and OATP1B3, and multidrug and toxin extrusion 1. Unlike ritonavir, COBI does not demonstrate any enzyme-inducing effects. The potential exists for multiple drug interactions when using COBI. Before COBI is administered, a patient’s medication profile should be carefully reviewed for potential interactions and overlapping toxicities with other drugs. Coadministration of medications that induce or inhibit CYP3A4 may respectively decrease or increase exposures of COBI and coformulated antiretroviral (ARV) medications. Coadministration of medications that are CYP3A4 substrates may result in clinically significant adverse reactions that are severe, life-threatening, or fatal, or may result in loss of therapeutic effect if dependent on conversion to an active metabolite due to CYP3A4 inhibition by COBI.¹
• Nucleoside reverse transcriptase inhibitors: COBI is a strong P-gp inhibitor; thus, a dose of tenofovir alafenamide (TAF) 10 mg combined with COBI produces tenofovir (TFV) exposures that are similar to those produced by TAF 25 mg without COBI.² COBI increases plasma TFV exposures by 23% when it is coadministered with TDF; thus, renal safety should be monitored in patients who are receiving this combination.^1,3
• Non-nucleoside reverse transcriptase inhibitors: Efavirenz, etravirine, and nevirapine should not be used with COBI.
• Protease inhibitors: Using COBI as a dual booster for elvitegravir (EVG) and darunavir (DRV) has been studied in people with and without HIV, and the evidence is conflicting. When EVG plus COBI plus DRV was administered to people without HIV, the trough concentration (C_trough) of EVG was 50% lower than the C_trough seen in people who received elvitegravir/cobicistat (EVG/c)/emtricitabine (FTC)/tenofovir disoproxil fumarate (TDF) without DRV.⁴ When EVG/c/FTC/TAF was administered with DRV to patients with HIV, both DRV and EVG concentrations were comparable to those seen in historic controls^5,6
• Integrase inhibitors: In one small study, dolutegravir (DTG) C_trough was 107% higher when DTG was administered with darunavir/cobicistat (DRV/c) than when it was administered with darunavir/ritonavir.⁷ Bictegravir (BIC) area under the curve increases 74% when BIC is administered with DRV/c.⁸
• Corticosteroids: Increased serum concentrations of corticosteroids can occur when corticosteroids and COBI are coadministered; this can lead to clinically significant adrenal suppression. Adrenal suppression occurs regardless of whether the corticosteroids are administered orally or by some other route (e.g., intranasal, inhaled, interlaminar, intraarticular) and regardless of whether the corticosteroids are administered routinely or intermittently. A possible exception is beclomethasone, which appears to be a relatively safe option with inhaled or intranasal administration.^9,10

Major Toxicities

• More common: Nausea, vomiting, diarrhea, abdominal pain, anorexia
• Less common (more severe): New onset renal impairment or worsening of renal impairment when used with TAF or TDF. Rhabdomyolysis; increased amylase and lipase levels.
• Case Report: One case report exists of a woman with low body weight (36 kg) and declining renal function who developed severe Type B lactic acidosis while on the combination of COBI, DRV, and non–dose-adjusted TDF/FTC. The woman’s TFV C_trough during this episode was found to be up to fivefold higher than trough values reported in adults with normal renal function. The woman’s FTC concentration was not measured.¹¹

Resistance

Not applicable because COBI has no antiviral activity.

Pediatric Use

Approval

COBI is a pharmacokinetic (PK) enhancer of ARV drugs that is available as a single agent or a component of fixed-dose combination products. COBI, as a component of Stribild, is approved by the U.S. Food and Drug Administration (FDA) at the adult dose for use in children and adolescents aged ≥12 years and weighing ≥35 kg.¹² The Panel on Antiretroviral Therapy and Medical Management of Children Living With HIV recommends limiting the use of Stribild to those with a sexual maturity rating of 4 or 5. COBI, as a component of Genvoya, is approved by the FDA at the adult dose for use in children weighing ≥25 kg.¹³ The FDA has not approved COBI as a component of Genvoya for use in children weighing <25 kg, but a PK, safety, and efficacy study has been conducted with a low-dose tablet in children weighing ≥14 kg to <25 kg (see the Elvitegravir section). COBI alone (as Tybost) has been discontinued, and no generic standalone tablet formulation of COBI exists.¹ Prezcobix PED dispersible tablets are available for HIV treatment in children aged ≥3 years and weighing ≥15 kg.¹⁵ COBI, coformulated with ATV (as Evotaz),¹⁴ is approved by the FDA at the adult dose for use in children and adolescents weighing ≥35 kg. COBI, coformulated with DRV (as Prezcobix)¹⁵ and as a component of Symtuza,¹⁶ is approved by the FDA in children and adolescents weighing ≥25 kg. COBI, as a component of Symtuza, is approved by the FDA at the adult dose in children and adolescents weighing ≥40 kg.

References

1. Cobicistat (Tybost) [package insert]. Food and Drug Administration. 2025. Available at: https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/203094s017s018lbl.pdf.
2. Ramanathan S, Wei X, Custudio J, et al. Pharmacokinetics of a novel EVG/COBI/FTC/GS-7340 single tablet regimen. Abstract O-13. Presented at: 13th International Workshop on Clinical Pharmacology of HIV Therapy. 2012. Barcelona, Spain. Available at: https://www.natap.org/2012/pharm/Pharm_24.htm.
3. Custodio J, Garner W, Jin F, et al. Evaluation of the drug interaction potential between the pharmacokinetic enhancer and tenofovir disoproxil fumarate in healthy subjects. Presented at: 14th International Workshop on Clinical Pharmacology of HIV Therapy. 2013. Amsterdam, The Netherlands. Available at: https://www.natap.org/2013/Pharm/Pharm_15.htm.
4. Ramanathan S, Wang H, Szwarcberg J, Kearney BP. Safety/tolerability, pharmacokinetics, and boosting of twice-daily cobicistat administered alone or in combination with darunavir or tipranavir. Abstract P-08. Presented at: 13th International Workshop on Clinical Pharmacology of HIV Therapy. 2012. Barcelona, Spain. Available at: https://www.natap.org/2012/pharm/Pharm_28.htm.
5. Harris M, Ganase B, Watson B, et al. HIV treatment simplification to elvitegravir/cobicistat/emtricitabine/tenofovir disproxil fumarate (E/C/F/TDF) plus darunavir: a pharmacokinetic study. AIDS Res Ther. 2017;14(1):59. Available at: https://pubmed.ncbi.nlm.nih.gov/29096670.
6. Huhn GD, Tebas P, Gallant J, et al. A randomized, open-label trial to evaluate switching to elvitegravir/cobicistat/emtricitabine/tenofovir alafenamide plus darunavir in treatment-experienced HIV-1-infected adults. J Acquir Immune Defic Syndr. 2017;74(2):193-200. Available at: https://pubmed.ncbi.nlm.nih.gov/27753684.
7. Gervasoni C, Riva A, Cozzi V, et al. Effects of ritonavir and cobicistat on dolutegravir exposure: when the booster can make the difference. J Antimicrob Chemother. 2017;72(6):1842-1844. Available at: https://pubmed.ncbi.nlm.nih.gov/28333266.
8. Zhang H, Custudio J, Wei X, et al. Clinical pharmacology of the HIV integrase strand transfer inhibitor bictegravir. Presented at: Conference on Retrovirsues and Opportunistic Infections. 2017. Seattle, WA. Available at: https://www.croiconference.org/sessions/clinical-pharmacology-hiv-integrase-strand-transfer-inhibitor-bictegravir.
9. Saberi P, Phengrasamy T, Nguyen DP. Inhaled corticosteroid use in HIV-positive individuals taking protease inhibitors: a review of pharmacokinetics, case reports and clinical management. HIV Med. 2013;14(9):519-529. Available at: https://pubmed.ncbi.nlm.nih.gov/23590676.
10. Boyd SD, Hadigan C, McManus M, et al. Influence of low-dose ritonavir with and without darunavir on the pharmacokinetics and pharmacodynamics of inhaled beclomethasone. J Acquir Immune Defic Syndr. 2013;63(3):355-361. Available at: https://pubmed.ncbi.nlm.nih.gov/23535292.
11. Isoda A, Mihara M, Matsumoto M, Sawamura M. Severe lactic acidosis during tenofovir disoproxil fumarate and cobicistat combination for HIV patient. BMJ Case Rep. 2023;16(11). Available at: https://pubmed.ncbi.nlm.nih.gov/37923339.
12. Stribild (elvitegravir, cobicitstat, emtricitabine, tenofovir disaproxil fumarate) [package insert]. Food and Drug Administration. 2021. Available at: https://www.accessdata.fda.gov/drugsatfda_docs/label/2021/203100s036lblet.pdf.
13. Genvoya (elvitegravir/cobicistat/emtricitabine/tenofovir alafenamide) [package insert]. Food and Drug Administration. 2022. Available at: https://www.accessdata.fda.gov/drugsatfda_docs/label/2022/207561s029lbl.pdf.
14. Evotaz (atazanavir/cobicistat) [package insert]. Food and Drug Administration. 2022. Available at: https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/206353s009lbl.pdf
15. Prezcobix (darunavir/cobicistat) [package insert]. Food and Drug Administration. 2022. Available at: https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/205395s028lbl.pdf
16. Symtuza (darunavir, cobicistat, emtricitabine, and tenofovir alafenamide) [package insert]. Food and Drug Administration. 2022. Available at: https://www.accessdata.fda.gov/drugsatfda_docs/label/2023/210455s023lbl.pdf