Highly sensitive UPLC-MS/MS method for the quantification of paromomycin in human plasma

A highly sensitive method was developed to quantitate the antileishmanial agent paromomycin in human plasma, with a lower limit of quantification of 5 ng/mL. Separation was achieved using an isocratic ion-pair ultra-high performance liquid chromatographic (UPLC) method with a minimal concentration of heptafluorobutyric acid, which was coupled through an electrospray ionization interface to a triple quadrupole - linear ion trap mass spectrometer for detection. The method was validated over a linear calibration range of 5 to 1000 ng/mL (r²≥0.997) with inter-assay accuracies and precisions within the internationally accepted criteria. Volumes of 50 μL of human K₂EDTA plasma were processed by using a simple protein precipitation method with 40 μL 20 % trichloroacetic acid. A good performance was shown in terms of recovery (100 %), matrix effect (C.V. ≤ 12.0 %) and carry-over (≤17.5 % of the lower limit of quantitation). Paromomycin spiked to human plasma samples was stable for at least 24 h at room temperature, 6 h at 35 °C, and 104 days at -20 °C. Paromomycin adsorbs to glass containers at low concentrations, and therefore acidic conditions were used throughout the assay, in combination with polypropylene tubes and autosampler vials. The assay was successfully applied in a pharmacokinetic study in visceral leishmaniasis patients from Eastern Africa.

Disposition of antimony and aminosidine combination after multiple subcutaneous injections in dogs

The disposition of a combination of antimony (Sbv) (12.8 mg/kg) and aminosidine (AM) (10 mg/kg) in 10 healthy Beagle dogs after multiple subcutaneous injections is described. Sbvplasma concentrations were determined by atomic absorption spectrometry, and AM by ion-pair liquid chromatography, using a fluorimetric detector. Sbvreached Cmaxat 60 min, and for about 1 h plasma levels were homogeneously stabilized between 10.78 and 11.76 microgram/mL; by 12 h, Sbvplasma concentrations were close to the detection limit (0.3 microgram/mL). AM Cmaxvalues were recorded after 1 h (30.6+/-3.11 microgram/mL, mean +/- SD), and plasma levels reached values close to the detection limit (0.15 microgram/mL) between 7 and 8 h after injection. Sbvkinetic parameters did not appear modified by the presence of AM. Moreover, repeated injections of the combination did not modify the kinetic behaviour of the two drugs and did not alter the renal function of the animals. The superimposition analysis of the Sbvdata suggests that a twice daily injection of the metal at a dose of 12.8 mg/kg would be sufficient to maintain inhibitory Sbvconcentrations similar to those recorded in humans.

Determination of paromomycin in human plasma and urine by reversed-phase high-performance liquid chromatography using 2,4-dinitrofluorobenzene derivatization

A sensitive high-performance liquid chromatographic method for the determination of paromomycin in human plasma and urine was developed. Paromomycin was quantitated following pre-column derivatization with 2,4-dinitrofluorobenzene (DNFB). The chromatographic separation was carried out on a C18 column at 50 degrees C using a mobile phase consisting of 64% methanol in water adjusted to pH 3.0 with phosphoric acid. The eluents were monitored by UV detection at 350 nm. The linearity of response for paromomycin was demonstrated at concentrations from 0.5 to 50 microg/ml in plasma and 1 to 50 microg/ml in urine. The relative standard deviation of the assay procedure is less than 5%.

Pharmacokinetics of intramuscularly administered aminosidine in healthy subjects

Aminosidine is an older, broad-spectrum aminoglycoside antibiotic that has been shown to be effective in in vitro and animal models against multiple-drug-resistant tuberculosis and the Mycobacterium avium complex. The objective of this randomized, parallel trial was to characterize the single-dose pharmacokinetics of aminosidine sulfate in healthy subjects (eight males, eight females). Sixteen adults (mean [+/- standard deviation] age, 27.6 +/- 5.6 years) were randomly allocated to receive a single, intramuscular aminosidine sulfate injection at a dose of 12 or 15 mg/kg of body weight. Serial plasma and urine samples were collected over a 24-h period and used to determine aminosidine concentrations by high-performance liquid chromatographic assay. A one-compartment model with first-order input, first-order output, and a lag time (Tlag) and with a weighting factor of 1/y2 best described the data. Compartmental and noncompartmental pharmacokinetic parameters were estimated with the microcomputer program WinNonlin. One subject was not included (15-mg/kg group) because of the lack of sampling time data. On average, subjects attained peak concentrations of 22.4 +/- 3.2 microg/ml at 1.34 +/- 0.45 h. All subjects had plasma aminosidine concentrations below 2 microg/ml at 12 h, and all but two subjects (one in each dosing group) had undetectable plasma aminosidine concentrations at 24 h. The dose-adjusted area under the concentration-time curve from 0 h to infinity of aminosidine was identical for the 12- and 15-mg/kg groups (9.29 +/- 1.5 versus 9.29 +/- 2.2 microg x h/ml per mg/kg; P = 0.998). Similarly, no significant differences (P > 0.05) were observed between dosing groups for peak aminosidine concentration in plasma, time to peak aminosidine concentration in plasma, Tlag, apparent clearance, renal clearance, elimination rate constant, and elimination half-life. A significant difference was observed for the volume of distribution (0.35 versus 0.41 liters/kg; P = 0.037) between the 12 and 15 mg/kg dosing groups. Now that comparable pharmacokinetic profiles between dosing groups have been demonstrated, therapeutic equivalency testing via in vitro pharmacokinetic and pharmacodynamic modelling and randomized clinical trials in humans should be conducted.

Topical treatment of cutaneous leishmaniasis

Sixty-seven patients, 19 females and 48 males, 4-66 years old, suffering from lesions of cutaneous leishmaniasis were treated topically with an ointment comprising 15% paromomycin sulfate and 12% methylbenzethonium chloride in white soft paraffin (P-ointment, U.K. patent GB117237A). After 10 days of treatment, twice daily, the lesions in 72% of the treated patients were free of parasites, 15% became free within an additional 20 days, without further treatment, and 13% failed to respond. Pigmentation developed in 18% of the treated lesions and inflammation of varying degree was associated with the treatment. These developments did not affect the clinical healing process which was generally completed in a period of 10-30 days after termination of treatment. In addition, 94% of the treated lesions healed with little or no scarring. No adverse clinical or laboratory side effects were observed except for a burning sensation at the site of treatment. Parasites isolated from patients who failed to respond to topical treatment were found to be susceptible to PR-MBCl in both in vitro infected macrophages and in vivo in experimentally infected BALB/c mice.