I would recommend screening the patient to see if they are taking the medication at the same time each day and if they are taking any over the counter supplements. The elimination half life is longer for bictegravir, however, shorter for tenofovir AF and emtricitabine; Any multivitamin, minerals, antacids, calcium, iron should be separated from the drug by taking the Biktarvy 2 hours before or 6 hours after. Depending on the source of information, some sources would state ok to take together, however, data also is available showing up to a 43% drop in AUC. I mark the labels as Biktarvy 2 hours before or 6 hours after as the DHHS guidelines are also not consistent depending on which section you review (INSTI as a class, INSTI DDI, etc.) Ideally, would screen for St. Johns Wort, any herbals, teas or natural products for induction concerns.
I would recommend also checking the bottle (physically) to ensure the strength is correct. Recently ISMP reported mix-up of adult and pediatric Biktarvy and the wrong strength had actually been dispensed as pediatric strength for an adult patient as the bottles appear similar. This is to check if the pharmacy dispensed the correct product by physically verifying the bottle. We have also received the wrong strength directly prescribed by clinics to the pharmacy, likely by prescribers who are overworked, inadequately staffed. I would not be surprised if a 'Biktarvy' prescription called into a pharmacy without a strength listed (I have received these electronically as well as verbally) gets entered incorrectly by a pharmacy technician and gets incorrectly checked by a pharmacist that is not familiar with HIV medications.
HIV-1 Virologic Rebound Due to Coadministration of Divalent Cations and Bictegravir
|PubMed Central (PMC)
|HIV-1 Virologic Rebound Due to Coadministration of Divalent Cations and Bictegravir
|A potential drug-drug interaction exists between divalent and trivalent cations (Ca 2+, Fe 3+, Mg 2+, Al 3+, Zn 2+) and HIV-1 integrase strand transfer inhibitors (INSTIs). There are limited case reports describing the clinical significance of this potential interaction and none to our knowledge identifying zinc co-administration with INSTIs.
| View this on PubMed Central (PMC) >
Debbie Nguyen, PharmD, AAHIVP
Sent: 05-24-2023 19:49
From: Ayse Elif Ozdener
Subject: Patient Question
I want to ask for your expert opinion about a patient we are having trouble with in our outpatient clinic.
The patient is currently taking Biktarvy and has been on this regimen for many months. The patient is adamant that they are adherent to therapy. This is confirmed with the pharmacy and pill counting. The patient stores the Biktarvy in a cool, dry place, and takes it correctly. Despite this, the patient has not be able to achieve an undetectable viral load. He persistently has a low level viremia, mostly below 500 copies/mL. He came to us with AIDS with a CD4 count less than 100 cells/mm3. His CD4 count now is >200 cells/mm3. He has not other infections. Genosure Archive results show he is pansensitive. We have not been able to obtain PhenoSense results because his viral load is too low. Recently, a healthcare provider on our HIV team decided to add Prezcobix to the Biktarvy to see if the additional antiretoviral can get the patient to undetectable levels. Believe it or not, the patient is still not undetectable. I am not sure what to do next. Any ideas would be very helpful!
Thank you in advance for reading this message and your contributions.
Elif Özdener-Poyraz, PharmD, MPH, BCACP, AAHIVP
Ambulatory Care Pharmacist