Sensitive LC-MS/MS Methods for Amphotericin B Analysis in Cerebrospinal Fluid, Plasma, Plasma Ultrafiltrate, and Urine: Application to Clinical Pharmacokinetics.

Neurocryptococcosis, a meningoencephalitis caused by Cryptococcus spp, is treated with amphotericin B (AmB) combined with fluconazole. The integrity of the brain-blood barrier and the composition of the cerebrospinal fluid (CSF) may change due to infectious and/or inflammatory diseases such as neurocryptococcosis allowing for the penetration of AmB into the central nervous system. The present study aimed to develop LC-MS/MS methods capable of quantifying AmB in CSF at any given time of the treatment in addition to plasma, plasma ultrafiltrate, with sensitivity compatible with the low concentrations of AmB reported in the CSF. The methods were successfully validated in the four matrices (25 µl, 5-1,000 ng ml-1 for plasma or urine; 100 µl, 0.625-250 ng ml-1 for plasma ultrafiltrate; 100 µl, 0.1-250 ng ml-1 for CSF) using protein precipitation. The methods were applied to investigate the pharmacokinetics of AmB following infusions of 100 mg every 24 h for 16 days administered as a lipid complex throughout the treatment of a neurocryptococcosis male patient. The methods allowed for a detailed description of the pharmacokinetic parameters in the assessed patient in the beginning (4th day) and end of the treatment with AmB (16th day), with total clearances of 7.21 and 4.25 L h-1, hepatic clearances of 7.15 and 4.22 L h-1, volumes of distribution of 302.94 and 206.89 L, and unbound fractions in plasma ranging from 2.26 to 3.25%. AmB was quantified in two CSF samples collected throughout the treatment with concentrations of 12.26 and 18.45 ng ml-1 on the 8th and 15th days of the treatment, respectively. The total concentration of AmB in plasma was 31 and 20 times higher than in CSF. The unbound concentration in plasma accounted for 77 and 44% of the respective concentrations in CSF. In conclusion, the present study described the most complete and sensitive method for AmB analysis in plasma, plasma ultrafiltrate, urine, and CSF applied to a clinical pharmacokinetic study following the administration of the drug as a lipid complex in one patient with neurocryptococcosis. The method can be applied to investigate the pharmacokinetics of AmB in CSF at any given time of the treatment.

Total, renal and hepatic clearances of doxorubicin and formation clearance of doxorubicinol in patients with breast cancer: Estimation of doxorubicin hepatic extraction ratio.

Doxorubicin (DOX) is a cytotoxic drug which has remained as an essential component of chemotherapy regiment for breast cancer. The cardiotoxicity of DOX is related to the accumulation of its main metabolite doxorubicinol (DOXOL) in the cardiac tissue. Although the pharmacokinetics of DOX shows high interindividual variability, there are no significant covariates to improve dose adjustment. The present study reports the pharmacokinetics of both DOX and DOXOL in a homogeneous population of young female patients with breast cancer (n = 12) making use of a standardized drug association, evaluated in the very first chemotherapy cycle, using plasma and urine data that allowed the calculation of the renal clearance of DOX, the formation clearance of DOXOL and the hepatic clearance of DOX. The extensive data availability also made it possible to estimate the hepatic extraction ratio of DOX for the investigated population, as well as to determine DOXOL unbound fraction in plasma for the first time in humans. DOX and DOXOL simultaneous analysis in plasma, plasma ultrafiltrate, and urine were performed by liquid chromatography coupled to mass spectrometry (LC-MS/MS). The pharmacokinetics profile of both DOX and DOXOL showed high variability (geometric coefficient of variation of area under the plasma concentration versus time curve extrapolated to infinity was approximately 215 %). The geometrics means were 0.26 for DOXOL/DOX AUC ratio, 15 % and 17 % for unbound fractions of DOX and DOXOL, respectively, 30.70 L⋅h-1 for total clearance, 0.66 L⋅h-1 for renal clearance, 29.97 L⋅h-1 for hepatic clearance and 0.39 L⋅h-1 for the formation clearance of the metabolite DOXOL. The 95 % confidence interval of the estimated hepatic extraction ratio of DOX ranged from 0.14 to 0.79, which characterizes DOX as a drug of low, intermediate or high hepatic extraction ratio.