High performance liquid chromatographic assay for the determination of Protease Inhibitors (PIs) and Non-nucleoside Reverse Transcriptase Inhibitors (NNRTIs) in human plasma.

Objective: To develop and validate a high performance liquid chromatography (HPLC) method for simultaneous quantitative determination of five HIV protease inhibitors (PIs): indinavir (IDV), lopinavir (LPV), nelfinavir (NFV), ritonavir (RTV), saquinavir (SQV), and two non-nucleoside reverse transcriptase inhibitors (NNRTIs): nevirapine (NVP), and efavirenz (EFV) in human plasma. Methods: A sample of 200 µL of plasma and an internal standard were extracted with tert-butyl methyl ether. The compounds were separated on a reversed-phase C18 column with gradient phase of 25 mM phosphate buffer (pH 4.9) and acetonitrile. The limit of quantation, accuracy, precision, specificity, stability and recovery were tested. Results: The lower limit of quantitation for all drugs was 75 ng/mL. The standard curve was linear in the range of 75 ng/mL to 20,000 ng/mL. Intra-day and inter-day variability ranged from 0.1% to 2.4% and 0.3% to 4.1%, respectively. Accuracy ranged from 98.4%-102.4% for three quality controls (75, 100, and 1,000 ng/mL) for all drugs measured. The extraction recovery ranged from 98.7%-101.3%. Conclusion: This method provides a simple, accurate, and precise method for monitoring of plasma concentrations of five PIs and two NNRTIs in the case of weak economy and out of date instrumental limitations.

Rapid determination of nevirapine in human plasma by high- performance liquid chromatography.

Objective: To develop and validate a high-performance liquid chromatography (HPLC) method for the determination of nevirapine in human plasma. Methods: A plasma sample and an internal standard were extracted with tert.-butyl methyl ether and determined nevirapine concentration by HPLC method. The limit of quantitation (LOQ), accuracy, precision, specificity, stability and recovery were tested for method validation. Results: Standard curve was linear in the range 0.1 ตg/mL to 20 ตg/mL. The limit of quantitation was 0.1 ตg/ml. Coefficients of variation (CV) of intraday and inter-day precision were less than 4 %. Accuracy was range from 97-101%. The extraction recovery was range from 94-112 %. Conclusion: A rapid, sensitive and specific HPLC method was developed and can be used for determination of plasma nevirapine concentration in adult and pediatric patients infected with HIV.

Vaccination against hepatitis B virus: are Thai medical students sufficiently protected?

Medical students are frequently at risk of being infected by hepatitis B virus (HBV) via occupational exposure to infected blood or body fluids. In 2002, the Faculty of Medicine, Siriraj Hospital provided screening tests for HBV serology to all medical students for a vaccination campaign against the infection. There were 1,165 medical students tested. Eight hundred and eleven (69.6%) students had immunity by previous vaccination, but more importantly 212 (18.2%) had no immunity and required vaccination. Most of the students who needed to be vaccinated were in the pre-clinical year (82.5%). Moreover, the students in the pre-clinical year who had previous vaccination had a 2.2 times greater risk of having negative anti-HBs than the students in the clinical year (OR = 2.2, 95% CI = 1.4-3.5). This is because they might have been vaccinated when they were young and the antibody waned overtime.

Amikacin: Area under curve for once daily dose and its correlation with plasma concentration at six hours post infusion.

Aminoglycosides are commonly used for gram-negative septicemia. Formerly, peak and trough plasma levels were the monitoring parameters for conventional dose which was every eight hours. At present the recommended dose is once daily and the recommended monitoring parameters are the area under concentration time curve and the six-hour (range 146-180) for the area under curve and 6.79 milligrams per liter (range 5.6-7.9) for the six-hour plasma concentration post-infusion. The correlation of the area under curve and the six-hour plasma concentration post-infusion was reported in a linear equation with significance.