Determination of Nevirapine and Efavirenz in Plasma Using GC/MS in Selected Ion Monitoring Mode

A fast-screening dispersive liquid-liquid microextraction-gas chromatography-mass spectrometry method applied to the determination of efavirenz in human plasma samples

We demonstrate the suitability of a fast, green, easy-to-perform, and modified sample extraction procedure, i.e., dispersive liquid-liquid microextraction (DLLME) for the determination of efavirenz (EFV) in human plasma. Data acquisition was done by gas chromatography-mass spectrometry (GC-MS) in the selected ion monitoring (SIM) mode. The simplicity of the method lies in, among others, the avoidance of the use of large organic solvent volumes as mobile phases and non-volatile buffers that tend to block the plumbing in high-performance liquid chromatography (HPLC). Chromatographic and mass spectral parameters were optimized using bovine whole blood for matrix matching due to insufficient human plasma. Method validation was accomplished using the United States Food and Drug Administration (USFDA) 2018 guidelines. The calibration curve was linear with a dynamic range of 0.10-2.0 μg/mL and an R² value of 0.9998. The within-run accuracy and precision were both less than 20% at the lower limit of quantification (LLOQ) spike level. The LLOQ was 0.027 μg/mL which compared well with some values but was also orders of magnitude better than others reported in the literature. The percent recovery was 91.5% at the LLOQ spike level. The DLLME technique was applied in human plasma samples from patients who were on treatment with EFV. The human plasma samples gave concentrations of EFV ranging between 0.14-1.00 μg/mL with three samples out of seven showing concentrations that fell within or close to the recommended therapeutic range.

Efavirenz in human breast milk, mothers', and newborns' plasma

BACKGROUND AND METHODS

Highly active antiretroviral therapy with efavirenz (EFV) has been prescribed to HIV-positive pregnant women in Rwanda (HIV status 1 and CD4 cell count > 350 cells/mm) during the last trimester of pregnancy and for 6 months after delivery. The EFV concentrations in maternal plasma, breast milk and in newborns' plasma of 13 women and their children between 6 weeks and 6 months post partum are reported.

RESULTS

Results show a mean EFV plasma concentration of 6.55 mg/L in maternal plasma, 3.51 mg/L in skim milk, and 0.85 mg/L in infant plasma. Significant linear correlations between maternal plasma and skim milk (r = 0.8666, P < 0.0001) and between skim milk and infant plasma (r = 0.6646, P < 0.02) were found, but no significant correlation was observed between maternal and infant plasma concentrations (P > 0.05).

CONCLUSIONS

After 6 months of breast-feeding, no child out of the 13 had been infected with HIV and all had good psychomotor and growth development. Our results suggest that EFV may be an alternative to nevirapine (NVP) during the third trimester of pregnancy and during the breast-feeding period. Further studies on larger groups of newborns will be necessary to get a better understanding of possible prophylactic protection of the newborns by highly active antiretroviral therapy with EFV given to the mothers.

Development of a highly efficient extraction technique and specific multiplex assay for measuring antiretroviral drug concentrations in breast milk

Understanding the pharmacology of drugs in breast milk is important for the health of both mother and baby. Current methods to measure drug concentrations in breast milk are not easily validated for precision or accuracy, primarily because of suboptimal sample clean-up. We report here an optimized clean-up method to remove both proteins and fat from milk, thereby enhancing the extraction efficiency of antiretroviral drugs. Recoveries were consistently above 91% for all drugs, demonstrating that this method successfully and reliably released drugs from fat globules. With use of 200 muL of human breast milk, an high-performance liquid chromatography/ultraviolet method for simultaneously detecting lamivudine, stavudine, zidovudine, and nevirapine was validated over the range of 20 to 20,000 ng/mL. Intra- and interday precision (average percent relative standard deviation) and accuracy (average percent deviation from nominal) was less than 3.6% and 7.5%, respectively. Intra- and interday accuracy (average percent deviation from nominal) was less than 0.25% and 1.3%, respectively. This novel method efficiently, reliably, and accurately measured antiretroviral drugs in breast milk and can be applied to any matrix containing fat and protein.

Efavirenz and Nevirapine in HIV-1 Infection

Nevirapine and efavirenz are nonnucleoside reverse transcriptase inhibitors used in antiretroviral regimens to treat HIV infection. Therapeutic drug monitoring in patients on antiretroviral regimens that include these agents has been suggested to be beneficial in terms of efficacy and toxicity. Various analytical methods are available to quantify nevirapine and efavirenz concentrations. A previously published, nine-step, decision-making algorithm has been used to evaluate the utility of therapeutic drug monitoring of efavirenz and nevirapine. A relationship has been found between efavirenz concentrations and toxicity and between nevirapine concentrations and virological efficacy. For efavirenz, the recommended therapeutic range is 1-4 mg/L; for nevirapine, minimum trough concentrations of >3.4 mg/L have been suggested. Both drugs have demonstrated interindividual pharmacokinetic variability. The pharmacokinetic parameters of nevirapine vary in female patients, patients coinfected with hepatitis B virus, and patients from different geographical locations. The pharmacokinetic parameters of efavirenz have also been shown to vary depending on patients' race, baseline bilirubin level, and geographical location. Drug interactions and resistance mutations can also be confounders in the pharmacokinetic parameters of these drugs. Coinfection with hepatitis C can also contribute to increased drug concentrations. The risk of hepatotoxicity can be increased in the presence of elevated nevirapine concentrations. As patients with HIV-1 infection will be managed with different combinations of antiretroviral regimens over the course of their lives, the limitations of having only four drug classes from which to choose make it even more important to maximise the usefulness of each of these drug classes. The available evidence suggests that therapeutic drug monitoring of efavirenz and nevirapine may contribute to the clinician's ability to evaluate efficacy and safety in patients taking these drugs. Patients at risk of toxicity from drug interactions or disease interactions and patients who may be noncompliant may gain the greatest benefit from therapeutic drug monitoring of efavirenz and nevirapine.