The use of quantitative clinical pharmacology approaches to support moxidectin dosing recommendations in lactation.

Moxidectin is approved by the US Food and Drug Administration (US FDA) for the treatment of onchocerciasis (river-blindness) due to Onchocerca volvulus in patients aged 12 years and older. In onchocerciasis-endemic areas, mass drug administration (MDA) programs with ivermectin, with or without vector control, aim to control the disease, reduce morbidity, interrupt transmission, and more recently, achieve elimination. Moxidectin has the potential to be used in MDA programs. In countries where onchocerciasis is endemic, infants are often breastfed up to the age of 2 years, suggesting that some women are likely to be lactating during such periodic MDA programs. Quantitative analyses of non-clinical and clinical data using non-compartmental analysis and population based pharmacokinetic (popPK) modeling as well as physiologically based pharmacokinetic modeling (PBPK) were performed to determine the amount of moxidectin excreted in breast milk and subsequent exposures in the infant. The results of the analyses were similar. Concentrations of moxidectin in breast milk followed a similar pattern to those in plasma, with maximum concentrations occurring approximately 4 hours after dosing followed by a rapid decline in both breast milk and plasma. As early as two days after dosing, concentrations of moxidectin in breast milk were below the threshold for acceptable daily intake levels established by the European Medicines Agency (EMA) and FDA for secondary exposures from veterinary use, and below the WHO recommended relative infant dose (RID) safety threshold. The analyses were conducted to support prescribers and policy makers on dosing recommendations for moxidectin in lactation.

Pharmacokinetics of sulfobutylether-ß-cyclodextrin (SBECD) in subjects on hemodialysis.

BACKGROUND: The disposition of sulfobutylether-ß-cyclodextrin (SBECD), the solubilizing excipient in intravenous (i.v.) voriconazole, was assessed in seven male subjects with end-stage renal disease on hemodialysis and six subjects with normal renal function. METHODS: All subjects received twice-daily i.v. voriconazole at the standard voriconazole dose [6 mg/kg (96 mg/kg SBECD) every 12 h (Q12h) on Day 1 followed by 3 mg/kg (48 mg/kg SBECD) Q12h on Days 2-4, with a single i.v. dose on the morning of Day 5]. Subjects were sampled at selected pre-dose trough times, at selected times after infusions and intensively on Day 3 (non-dialysis) and Day 4 (dialysis with high-flux membranes). Compartmental analyses were performed by NONMEM. RESULTS: SBECD disposition was characterized by a two-compartment model. In renal failure, mean central (V(1)) and peripheral compartment volumes (V(2)) were 9.9 and 6.5 L, respectively. In normal subjects, V(1) and V(2) were 9.6 and 5.2 L, respectively; SBECD clearance (CL) was 130 mL/min. CL in renal failure off-dialysis was 2.6 and 48 mL/min during dialysis; mean half-life decreased from 79 to 5 h during dialysis (normal subjects: 2.1 h). CONCLUSION: Hemodialysis can significantly reduce levels of SBECD in subjects with end-stage renal disease.

Pharmacokinetics, safety, and tolerability of voriconazole in immunocompromised children.

The pharmacokinetics of voriconazole in children receiving 4 mg/kg intravenously (i.v.) demonstrate substantially lower plasma exposures (as defined by area under the concentration-time curve [AUC]) than those in adults receiving the same therapeutic dosage. These differences in pharmacokinetics between children and adults limit accurate prediction of pediatric voriconazole exposure based on adult dosages. We therefore studied the pharmacokinetics and tolerability of higher dosages of an i.v.-to-oral regimen of voriconazole in immunocompromised children aged 2 to <12 years in two dosage cohorts for the prevention of invasive fungal infections. The first cohort received 4 mg/kg i.v. every 12 h (q12h), then 6 mg/kg i.v. q12h, and then 4 mg/kg orally (p.o.) q12h; the second received 6 mg/kg i.v. q12h, then 8 mg/kg i.v. q12h, and then 6 mg/kg p.o. q12h. The mean values for the AUC over the dosing interval (AUCτ) for 4 mg/kg and 6 mg/kg i.v. in cohort 1 were 11,827 and 22,914 ng.h/ml, respectively, whereas the mean AUCτ values for 6 mg/kg and 8 mg/kg i.v. in cohort 2 were 17,249 and 29,776 ng.h/ml, respectively. High interpatient variability was observed. The bioavailability of the oral formulation in children was approximately 65%. The safety profiles were similar in the two cohorts and age groups. The most common treatment-related adverse event was increased gamma glutamyl transpeptidase levels. There was no correlation between adverse events and voriconazole exposure. In summary, voriconazole was tolerated to a similar degree regardless of dosage and age; the mean plasma AUCτ for 8 mg/kg i.v. in children approached that for 4 mg/kg i.v. in adults, thus representing a rationally selected dosage for the pediatric population.

Pharmacokinetics, safety and tolerance of voriconazole in renally impaired subjects: two prospective, multicentre, open-label, parallel-group volunteer studies.

BACKGROUND AND OBJECTIVES: Since little is known regarding the pharmacokinetics of voriconazole in renally impaired patients, two prospective, open-label, parallel-group volunteer studies were conducted to estimate the effect of renal impairment on the pharmacokinetics of oral voriconazole and intravenous voriconazole solubilized with sulphobutylether-beta-cyclodextrin (SBECD), respectively. METHODS: In study A, male subjects with no (n = 6), mild (n = 6), moderate (n = 6) or severe (n = 6) renal impairment received one 200 mg dose of oral voriconazole. Voriconazole plasma levels were periodically assessed until 48 hours post-dose. In study B, male subjects with no (n = 6) or moderate (n = 7) renal impairment received multiple doses of intravenous voriconazole solubilized with SBECD (6 mg/kg twice daily [day 1] then 3 mg/kg twice daily [days 2-6] followed by a final dose of 3 mg/kg on the morning of day 7) at an infusion rate of 3 mg/kg/h. Voriconazole plasma levels were periodically assessed until 36 hours following the final dose. Pharmacokinetics were determined by non-compartmental methods. RESULTS: The pharmacokinetics of voriconazole were unaffected in subjects with any degree of renal impairment in both studies. In study B, clearance of SBECD was proportional to creatinine clearance (r2 = 0.857). Although two subjects had >30% increase in serum creatinine from baseline, these changes did not correlate with SBECD trough levels (r2 = 0.053). The majority of subjects with moderate renal insufficiency were able to tolerate 7 days of intravenous voriconazole solubilized with SBECD. CONCLUSION: These data suggest that renal impairment does not affect the pharmacokinetics of voriconazole. Furthermore, in subjects with moderate renal impairment, there is a strong linear correlation between SBECD clearance and creatinine clearance, and elevated SBECD levels do not necessarily correlate with increased serum creatinine levels (an indicator of worsening renal function).