Pharmacokinetics and dosing regimen of aminosidine in the dog

Clinical Pharmacokinetics of Systemically Administered Antileishmanial Drugs

This review describes the pharmacokinetic properties of the systemically administered antileishmanial drugs pentavalent antimony, paromomycin, pentamidine, miltefosine and amphotericin B (AMB), including their absorption, distribution, metabolism and excretion and potential drug–drug interactions. This overview provides an understanding of their clinical pharmacokinetics, which could assist in rationalising and optimising treatment regimens, especially in combining multiple antileishmanial drugs in an attempt to increase efficacy and shorten treatment duration. Pentavalent antimony pharmacokinetics are characterised by rapid renal excretion of unchanged drug and a long terminal half-life, potentially due to intracellular conversion to trivalent antimony. Pentamidine is the only antileishmanial drug metabolised by cytochrome P450 enzymes. Paromomycin is excreted by the kidneys unchanged and is eliminated fastest of all antileishmanial drugs. Miltefosine pharmacokinetics are characterized by a long terminal half-life and extensive accumulation during treatment. AMB pharmacokinetics differ per drug formulation, with a fast renal and faecal excretion of AMB deoxylate but a much slower clearance of liposomal AMB resulting in an approximately ten-fold higher exposure. AMB and pentamidine pharmacokinetics have never been evaluated in leishmaniasis patients. Studies linking exposure to effect would be required to define target exposure levels in dose optimisation but have only been performed for miltefosine. Limited research has been conducted on exposure at the drug’s site of action, such as skin exposure in cutaneous leishmaniasis patients after systemic administration. Pharmacokinetic data on special patient populations such as HIV co-infected patients are mostly lacking. More research in these areas will help improve clinical outcomes by informed dosing and combination of drugs.

Pharmacokinetics and tolerability of aminosidine after repeated administrations using an optimal dose regimen in healthy dogs and in dogs with leishmaniosis

Optimisation of dose schedules of aminoglycosides is required in order to increase efficacy and prevent their toxicity. The objective of this study was to determine the pharmacokinetic profile and the safety of aminosidine in dogs with naturally occurring leishmaniosis and in healthy dogs after once daily administration. Six young-adult, male, healthy, Beagle dogs and 12 dogs with clinical signs of canine leishmaniosis without azotemia and proteinuria were included in the study. Diagnosis of the disease was confirmed by serology, parasitology and molecular techniques. Pharmacokinetics and evaluation of renal function after repeated (once daily for 21 consecutive days) subcutaneous administration of aminosidine, at the dose of 15 mg/kg b.w. in both the healthy and the diseased animals were compared. Concentrations of aminosidine were determined by high-performance liquid chromatography and pharmacokinetic analysis was performed by the non-compartmental method. No significant differences were observed between healthy and diseased dogs considering all pharmacokinetic parameters. In general, mean Cmax ranged between 46.41 and 54.32 μg/mL and between 38.69 and 40.73 μg/mL in healthy dogs and in dogs with canine leishmaniosis, respectively. No accumulation of the drug was observed in either group since total elimination of aminosidine and half-life lambda z were not modified throughout the administration period. Aminosidine was well tolerated in all dogs with no clinical and clinicopathological signs of nephrotoxicity. Once daily administration of high dose of aminoglycosides, resulted in effective serum concentrations and absence of nephrotoxicity.

In Vitro Skin Permeation and Retention of Paromomycin from Liposomes for Topical Treatment of the Cutaneous Leishmaniasis

Paromomycin (PA), a very hydrophilic antibiotic, has been tested as an alternative topical treatment against cutaneous leishmaniasis (CL). Although this treatment has shown promising results, it has not been successful in accelerating the recovery in most cases. This could be attributed to the low skin penetration of PA. Liposomal formulations usually provide sustained and enhanced drug levels in skin. The aim of this study was to prepare liposomal formulations containing PA and to investigate their potential as topical delivery systems of this antileishmanial. Large multilamellar vesicles (MLVs) were prepared by conventional solvent evaporation method. Large unilamellar vesicles (LUVs) were prepared by reverse-phase evaporation method. The lipids used were soybean phosphatidylcholine (PC) and PC:cholesterol (CH) (molar ratio 1:1). The skin permeation experiments across stripped and normal hairless mice skin were performed in modified Franz diffusion cells. The PA entrapment in LUV liposomes (20.4 +/- 2.2%) was higher than that observed for MLV liposomes (7.5 +/- 0.9%). Drug entrapment was 41.9 +/- 6.2% and 27.2 +/- 2.4% for PC and PC:CH LUV, respectively. The skin permeation was 1.55 +/- 0.31%, 1.29 +/- 0.40%, 0.20 +/- 0.08%, and 0.50 +/- 0.19% for PC LUV, PC:CH LUV, empty LUV +/- PA and aqueous solution, respectively. Controlled topical delivery, across stripped skin, was observed for PA entrapped in LUV liposomes.