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Does tenofovir influence efavirenz pharmacokinetics?
Margalida Rotger1, Sara Colombo, Hansjakob Furrer
1Institute of Microbiology, University Hospital, Lausanne, Switzerland.
A study found no clear pharmacokinetic interaction between tenofovir (TFV) and efavirenz (EFV). However, slow efavirenz metabolizers taking TFV showed higher drug levels, suggesting a potential interaction in this subgroup.
Area of Science:
- Pharmacology
- Drug Interactions
- Pharmacokinetics
Background:
- A previous report suggested a potential interaction between tenofovir (TFV) and efavirenz (EFV), leading to neuropsychiatric symptoms.
- This study investigates the pharmacokinetic interaction between TFV and EFV.
Purpose of the Study:
- To evaluate the pharmacokinetic interaction between tenofovir (TFV) and efavirenz (EFV).
- To assess cross-sectional and longitudinal data in individuals receiving EFV.
Main Methods:
- Analysis of pharmacokinetic data from 169 individuals receiving EFV.
- Comparison of efavirenz plasma area-under-the-curve (AUC) levels in patients receiving or not receiving TFV.
- Stratification of analysis based on CYP2B6 genotype (loss/diminished-function alleles).
Main Results:
- Overall EFV AUC levels were comparable between patients receiving and not receiving TFV.
- In individuals with two CYP2B6 loss/diminished-function alleles (slow metabolizers), EFV AUC was significantly higher when co-administered with TFV.
- A significant interaction was found between CYP2B6 genotype and TFV co-medication (P = 0.009).
Conclusions:
- No definitive pharmacokinetic interaction between TFV and EFV was established in the general study population.
- An interaction between TFV and EFV cannot be excluded in individuals who are slow EFV metabolizers due to CYP2B6 genotype.
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