Guest Post: Boost Your Knowledge and Avoid Drug Interactions This Allergy Season - What Every Pharmacist Needs to Know about Nasal Sprays and Boosted HIV Medications

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Guest Post:

Boost Your Knowledge and Avoid Drug Interactions This Allergy Season - What Every Pharmacist Needs to Know about Nasal Sprays and Boosted HIV Medications

This guest post highlights an important interaction between antiretroviral medications and intranasal corticosteroids. Pharmacists must be aware of these interactions when prescribing for minor ailments, providing therapeutic substitutions, and providing over-the-counter recommendations to patients. For support in managing drug interactions with antiretrovirals, pharmacists can call St. Paul’s Hospital Ambulatory Pharmacy at 1-888-511-6222 to consult with an HIV pharmacist.

Cobicistat and ritonavir are used to increase concentrations of select antiretrovirals for the treatment of HIV. As potent inhibitors of many cytochrome P450 isoenzymes, including CYP3A4, cobicistat and ritonavir not only boost levels of select antiretrovirals, but also the levels of other CYP3A4 substrates. As such, these pharmacokinetic boosters have a high propensity for drug-drug interactions (DDIs).1,2

Intranasal corticosteroids (INCS) are a preferred treatment for the symptoms of allergic rhinitis as they reduce inflammation of the nasal passages.3 The metabolism of various prescribed steroids is facilitated by the CYP3A4 isoenzyme.4 Inhibition of CYP3A4 by ritonavir or cobicistat can increase serum steroid concentrations, leading to Cushing’s syndrome and adrenal suppression.2-4

Despite non-systemic administration, intranasal, inhaled, intra-articular, and even ocular steroids have all been implicated in clinically significant interactions in people living with HIV receiving ritonavir or cobicistat.3-5 The risk of Cushing’s syndrome and adrenal suppression secondary to intranasal fluticasone in this context is well-documented, in-part due to fluticasone’s lipophilicity and  longer receptor binding half-life.3,4 In comparison to fluticasone, there are fewer published cases involving intranasal budesonide or mometasone and no published cases involving intranasal ciclesonide or triamcinolone; however, as these corticosteroids are also metabolized via CYP3A4, HIV-specific literature and drug interaction resources caution against co-administration and encourage consideration of safer alternatives.3,4,6,7 The preferred INCS in patients taking CYP3A4 inhibitors is beclomethasone, as it is minimally metabolized by CYP3A4 and less likely to lead to a clinically significant DDI, though monitoring for corticosteroid toxicity is still recommended.3,4,6,7

When providing care to a person with allergic rhinitis who is also taking ritonavir or cobicistat, pharmacists should try to avoid DDIs with INCS by considering alternative treatments (such as nasal saline irrigation or second-generation oral antihistamines8) or mitigate DDI risk by opting for intranasal beclomethasone used at the lowest dose and for the shortest duration required. If avoidance of the DDI is not feasible, the patient’s HIV care team should be notified so that they can assess the patient for a switch to an unboosted antiretroviral regimen and/or arrange for appropriate clinical and laboratory (i.e. morning cortisol) monitoring as necessary.4  

As of 2020, antiretrovirals dispensed in British Columbia (BC) appear on Pharmanet. It is pertinent for all pharmacists to recognize the heightened potential for DDIs associated with many antiretrovirals and always screen for DDIs when prescribing for minor ailments, providing therapeutic substitutions, and providing over-the-counter recommendations to patients. Pharmacists are encouraged to utilize the following HIV-specific resources to minimize the occurrence of DDIs:

HIV/HCV Drug Therapy Guide (https://hivclinic.ca/app/)
University of Liverpool (https://hiv-druginteractions.org/checker)

Both of the above resources also provide quick reference charts and drug interaction summary tables by therapeutic indication. Pharmacists seeking more information on DDIs between non-prescription products (including INCS) and antiretrovirals may refer to: BCCfE Pharmacovigilance Initiative Safety Alert (ARVs with OTCs) https://bccfe.ca/wp-content/uploads/2023/12/bc-cfe_safetyalert_no6_2017-final.pdf. Pharmacists across BC are also welcome to call St. Paul’s Hospital Ambulatory Pharmacy at 1-888-511-6222 to consult with an HIV pharmacist.

About the Authors

 

Shiying Yang, PharmD, ACPR

Clinical Pharmacist

Vancouver General Hospital

 

Sandra Chang, BSc(Pharm), ACPR, PharmD

Clinical Pharmacy Specialist, Quality Assurance

St. Paul’s Hospital Ambulatory Pharmacy/BC Centre for Excellence in HIV/AIDS

 

Erin Ready, BSc(Pharm), ACPR, MPH, AAHIVP

Clinical Pharmacy Specialist, HIV

St. Paul’s Hospital Ambulatory Pharmacy

References:
  1. Tybost. Product Monograph; 2020. [cited 2025 April 2]. Available from: https://pdf.hres.ca/dpd_pm/00056376.PDF
  2. Norvir. Product Monograph; 2025. [cited 2025 April 2]. Available from: https://www.abbvie.ca/content/dam/abbvie-dotcom/ca/en/documents/products...
  3. Seymour N, Robinson M, Richardson D, Mohammed H, Williams D, McGilligan JA. Prescribing intranasal steroids in HIV-positive patients: Systematic review of the literature. The Journal of Laryngology & Otology. 2021 Aug 13;135(9):755–8. doi:10.1017/s0022215121001791
  4. Elliot ER, Theodoraki A, Jain LR, Marshall NJ, Boffito M, Baldeweg SE, et al. Iatrogenic Cushing’s syndrome due to drug interaction between glucocorticoids and the ritonavir or cobicistat containing HIV therapies. Clinical Medicine. 2016 Oct;16(5):412–8. doi:10.7861/clinmedicine.16-5-412
  5. Lepik K, Barrios R [Internet]. BCCFE; 2010 [cited 2025 Jun 20]. Available from: https://bccfe.ca/wp-content/uploads/2023/12/cfe_safetyalert_no2_2010_06_...
  6. HIV/HCV Drug Therapy Guide. UHN- Toronto General Hospital, Immunodeficiency Clinic; 2022 [cited 2025 April 2]. Available from: https://app.hivclinic.ca/
  7. HIV Drug Interactions. University of Liverpool; 2023 [cited 2023 May 04]. Available from: https://www.hiv-druginteractions.org/
  8. Rosenfeld L, Keith PK, Quirt J, Small P, Ellis AK. Allergic rhinitis. Allergy Asthma Clin Immunol. 2024; 20(Suppl 3), 74. Available from: https://doi.org/10.1186/s13223-024-00923-6
Jun 27, 2025