Metabolism and interactions of antileprosy drugs.

Leprosy is a chronic infectious disease caused my Mycobacterium leprae that primarily affects peripheral nervous system and extremities and is prevalent in tropical countries. Treatment for leprosy with multidrug regimens is very effective compared to monotherapy especially in multibacillary cases. The three major antileprosy drugs currently in use are 4, 4'-diaminodiphenyl sulfone (DDS, dapsone), rifampicin, and clofazimine. During multidrug therapy, the potent antibiotic rifampicin induces the metabolism of dapsone, which results in decreased plasma half-life of dapsone and its metabolites. Furthermore, rifampicin induces its own metabolism and decreases its half-life during monotherapy. Rifampicin upregulates several hepatic microsomal drug-metabolizing enzymes, especially cytochrome P450 (CYP) family that in turn induce the metabolism of dapsone. Clofazimine lacks significant induction of any drug-metabolizing enzyme including CYP family and does not interact with dapsone metabolism. Rifampicin does not induce clofazimine metabolism during combination treatment. Administration of dapsone in the acetylated form (acedapsone) can release the drug slowly into circulation up to 75 days and could be useful for the effective treatment of paucibacillary cases along with rifampicin. This review summarizes the major aspects of antileprosy drug metabolism and drug interactions and the role of cytochrome P450 family of drug metabolizing enzymes, especially CYP3A4 during multidrug regimens for the treatment of leprosy.

Novel electrochemical biosensor based on PVP capped CoFe2O4@CdSe core-shell nanoparticles modified electrode for ultra-trace level determination of rifampicin by square wave adsorptive stripping voltammetry.

This work introduces a new electrochemical sensor based on polyvinyl pyrrolidone capped CoFe2O4@CdSe core-shell modified electrode for a rapid detection and highly sensitive determination of rifampicin (RIF) by square wave adsorptive stripping voltammetry. The new PVP capped CoFe2O4@CdSe with core-shell nanostructure was synthesized by a facile synthesis method for the first time. PVP can act as a capping and etching agent for protection of the outer surface nanoparticles and formation of a mesoporous shell, respectively. Another important feature of this work is the choice of the ligand (1,10-phenanthroline) for precursor cadmium complex that works as a chelating agent in order to increase optical and electrical properties and stability of prepared nanomaterial. The nanoparticles have been characterized by field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), UV-vis, photoluminescence (PL) spectroscopy, FT-IR, and cyclic voltammetry techniques. The PL spectroscopy study of CoFe2O4@CdSe has shown significant PL quenching by the formation of CoFe2O4 core inside CdSe, this shows that CoFe2O4 NPs are efficient electron acceptors with the CdSe. It is clearly observed that the biosensor can significantly enhance electrocatalytic activity towards the oxidation of RIF, under the optimal conditions. The novelty of this work arises from the new synthesis method for the core-shell of CoFe2O4@CdSe. Then, the novel electrochemical biosensor was fabricated for ultra-trace level determination of rifampicin with very low detection limit (4.55×10-17M) and a wide linear range from 1.0×10-16 to 1.0×10-7M. The fabricated biosensor showed high sensitivity and selectivity, good reproducibility and stability. Therefore, it was successfully applied for the determination of ultra-trace RIF amounts in biological and pharmaceutical samples with satisfactory recovery data.

Rifampicin attenuates the MPTP-induced neurotoxicity in mouse brain.

Rifampicin, an antibacterial drug, is highly effective in the treatment of tuberculosis and leprosy. Recently, it has been reported to have neuroprotective effects in in vitro and in vivo models. This study was designed to elucidate its neuroprotective effects against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neurotoxicity (known as an in vivo mouse model of Parkinson's disease). Mice were injected intraperitoneally (i.p.) with MPTP (10 mg/kg) four times at 1-h intervals, and brains were analyzed 3 or 7 days later. Rifampicin at 20 mg/kg (i.p., twice) had protective effects against MPTP-induced neuronal damage (immunohistochemical changes in tyrosine hydroxylase) in both the substantia nigra and striatum. Rifampicin also protected against the MPTP-induced depletions of dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) in the striatum. The maximal concentrations of rifampicin between 30 and 240 min after a single rifampicin injection (20 mg/kg, i.p.) were 2.6 microM (at 30 min) in plasma and 0.77 microM (at 60 min) in striatum. Next, the effects of rifampicin on oxidative stress [lipid peroxidation in mouse brain homogenates and free radical-scavenging activity against diphenyl-p-picrylhydrazyl (DPPH)] were evaluated to clarify the underlying mechanism. At 1 microM or more, rifampicin significantly inhibited both lipid peroxidation in the striatum and free radical production. These findings suggest that in mice, rifampicin can reach brain tissues at concentrations sufficient to attenuate MPTP-induced neurodegeneration in the nigrostriatal dopaminergic neuronal pathway, and that an inhibitory effect against oxidative stress may be partly responsible for its observed neuroprotective effects.

[Correlation between dose/plasma concentration and assessment of hepatic and renal changes in Wistar rats treated with the ROM scheme]. / Correlação entre dose/concentração plasmática e avaliação de alterações hepáticas e renais em ratos Wistar tratados com o esquema ROM.

Leprosy, a chronic granulomatous infectocontagious disease transmitted by Mycobacterium leprae, continues to be prevalent today, especially in underdeveloped countries and its paucibacillary form with a single lesion is being treated with rifampicin (600mg), ofloxacin (400mg) and minocycline (100mg) administered as a single dose (ROM scheme). Thus, the objective of the present study was to investigate the dose/plasma concentration correlation versus biochemical changes occurring in male Wistar rats receiving a single dose of rifampicin, ofloxacin and minocycline in mono- and polytherapy. Rifampicin and ofloxacin showed an increased concentration in plasma when administered in polytherapy, whereas minocycline was reduced, probably due to interference with its biotransformation and excretion. Biochemical analyses showed that rifampicin is probably responsible for hepatic and renal changes and that the medicamentous interactions involving the drug require individualized studies, especially when the drug is associated with ofloxacin and minocycline therapy.

Correlação entre dose/concentração plasmática e avaliação de alterações hepáticas e renais em ratos Wistar tratados com o esquema ROM / Correlation between dose/plasma concentration and assessment of hepatic and renal changes in Wistar rats treated with the ROM scheme

A hanseníase, doença crônica, granulomatosa, infecto-contagiosa, transmitida pelo Mycobacterium leprae, ainda se mantém prevalente nos dias atuais, principalmente em países subdesenvolvidos e a sua forma paucibacilar com lesão única, vem sendo tratada através da administração de rifampicina (600mg), ofloxacina (400mg) e minociclina (100mg), em dose única (esquema ROM). Assim, o objetivo deste trabalho foi investigar a correlação dose/concentração plasmática versus alterações bioquímicas na administração da rifampicina, ofloxacina e minociclina a ratos machos Wistar, em regime de dose única em mono e politerapia. Concluímos que a rifampicina e a ofloxacina sofreram um aumento na concentração plasmática quando administrados em politerapia, enquanto que a minociclina sofreu uma redução, provavelmente por interferências na biotransformação e excreção. Constatamos através das análises bioquímicas que a rifampicina provavelmente é a responsável por alterações hepáticas e renais, e que as interações medicamentosas envolvendo o fármaco exigem estudos individualizados principalmente quando o fármaco é usado associado a ofloxacina e minociclina.

Liquid chromatography/tandem mass spectrometric bioanalysis using normal-phase columns with aqueous/organic mobile phases - a novel approach of eliminating evaporation and reconstitution steps in 96-well SPE.

Bioanalytical methods using automated 96-well solid-phase extraction (SPE) and liquid chromatography with electrospray tandem mass spectrometry (LC/MS/MS) are widely used in the pharmaceutical industry. SPE methods typically require manual steps of drying of the eluates and reconstituting of the analytes with a suitable injection solvent possessing elution strength weaker than the mobile phase. In this study, we demonstrated a novel approach of eliminating these two steps in 96-well SPE by using normal-phase LC/MS/MS methods with low aqueous/high organic mobile phases, which consisted of 70-95% organic solvent, 5-30% water, and small amount of volatile acid or buffer. While the commonly used SPE elution solvents (i.e. acetonitrile and methanol) have stronger elution strength than a mobile phase on reversed-phase chromatography, they are weaker elution solvents than a mobile phase for normal-phase LC/MS/MS and therefore can be injected directly. Analytical methods for a range of polar pharmaceutical compounds, namely, omeprazole, metoprolol, fexofenadine, pseudoephedrine as well as rifampin and its metabolite 25-desacetyl-rifampin, in biological fluids, were developed and optimized based on the foregoing principles. As a result of the time saving, a batch of 96 samples could be processed in one hour. These bioanalytical LC/MS/MS methods were validated according to "Guidance for Industry - Bioanalytical Method Validation" recommended by the Food and Drug Administration (FDA) of the United States.

High-performance liquid chromatographic determination of rifapentine in serum using column switching.

A high-performance liquid chromatographic method with column switching has been developed for the determination of rifapentine in serum. The serum samples were injected onto a precolumn packed with Corasil RP C18 (37-50 microns) after simple dilution with an internal standard in a 1% ascorbic acid solution. Polar serum components were washed out using 0.05 M phosphate buffer. After valve switching, the concentrated drugs were eluted in the back-flush mode and separated by a mu Bondapak C18 column with acetonitrile-tetrahydrofuran-0.05 M phosphate buffer (pH 7.0) (42:5:53, v/v/v) as the mobile phase. The method showed excellent precision with good sensitivity and speed, and a detection limit of 0.1 microgram/ml. The total analysis time was less than 25 min and the mean coefficients of variation for intra- and inter-assay were less than 4.8%. The method has been successfully applied to serum samples from dogs after the oral administration of rifapentine.

Rifampin in drug-incorporated diet: effect of duration and temperature of storage. Relevance to drug-susceptibility testing in mice inoculated with M. leprae.

This paper is in two parts. Plasma concentrations of rifampin were assayed at 11 time points in 24 hr in mice fed one of three dosages of rifampin, either by gavage or by dietary incorporation. The drug-mixed diets had been stored for a maximum of 3 weeks at 4 degrees C or at room temperature (30 degrees C-35 degrees C). The peak concentration of rifampin produced by gavage was approximately 11/2 times higher than the maximum plasma concentration of the corresponding dosage in fresh diet. Plasma concentrations decreased with the increasing duration of storage of the drug-mixed diet, irrespective of whether the diet was stored at 4 degrees C or at room temperature. This decrease was less when the diet was stored at 4 degrees C than at room temperature. Drug levels were also assayed in another set of mice selected from ongoing drug-susceptibility experiments; these mice were fed a rifampin-incorporated diet stored at room temperature. The plasma concentrations in these mice, assayed at the time of foot pad harvest, were generally higher than in the 24-hr experiment. The harvest results from these mice were compared with the harvest results from a third set of mice, also from ongoing drug-susceptibility experiments, but fed a rifampin-mixed diet stored at 4 degrees C. Multiplication of Mycobacterium leprae in mouse foot pads was prevented by rifampin mixed in the diet at a dosage of greater than or equal to 0.003%, whether stored at room temperature or at 4 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Microbiological assay versus spectrophotometry for determination of rifampicin in urine.

A comparative study on the microbiological and spectrophotometric methods for estimation of rifampicin in urine was carried out in 15 individuals. The urinary levels of rifampicin were determined on 2nd, 8th and 15th days at 3 hour, 6 hour and 24 hour samples by the above methods after administration of 600 mg rifampicin. The results suggest that the microbiological assay is more sensitive than spectrophotometric method. The difference was highly significant in all the cases by paired t-test. Incidentally it was also noticed that urinary excretion of rifampicin was comparatively more on 15th day.

Evaluation of subdermal biodegradable implants incorporating rifampicin as a method of drug delivery in experimental tuberculosis of guinea pigs.

Conventional chemotherapy of tuberculosis and leprosy requires rifampicin to be administered orally. The long period of treatment and adverse side effects of the drug lead to poor compliance. To overcome this, subdermal implants incorporating rifampicin in pure and micro-encapsulated forms with biodegradable material were used as a new drug delivery system in experimental tuberculosis of guinea pigs. Two experiments were performed with 45-mg and 100-mg drug implants. Progress of infection was followed at intervals by studying necropsy scores and weights of the organs of predilection and levels of the drug in the blood were determined. There was a constant and sustained release of the drug in therapeutic concentrations for 30 and 50 days until the implants were completely assimilated without causing any damage to the implant site. The importance of multiple implants at long intervals is discussed.

Effect of clofazimine and dapsone on rifampicin (Lositril) pharmacokinetics in multibacillary and paucibacillary leprosy cases.

A comparative pharmacokinetic study of Lositril (rifampicin) was carried out in six multibacillary and twelve paucibacillary leprosy cases. The type of leprosy had no significant effect on rifampicin pharmacokinetics. The effect of dapsone and clofazimine when given separately and in combination was studied on rifampicin pharmacokinetics in each group of six patients. Within group comparison revealed that clofazimine reduced rifampicin absorption significantly (P less than 0.01) and prolonged the time to reach the peak serum concentration (P less than 0.01). Since MCR and Ke were also reduced significantly in RC group, as compared with RDC group (P less than 0.02 and P less than 0.05 respectively), no significant alteration was seen in overall Auc and Cmax, although t0.05 was increased significantly (P less than 0.02) in RC Group. Dapsone alone did not produce any significant alteration in rifampicin pharmacokinetics parameters, while dapsone with clofazimine reduced rifampicin 1h serum levels (P less than 0.05) and Auc (P less than 0.05) significantly. Of the three groups, except RC group, both RDC and RD groups were homogeneous Ka, avd, Cmax and Auc/t0.5 ratio of RC group were significantly different from those in RD group. While Ka and avd were significantly less (P less than 0.05 and less than 0.001 respectively) and Cmax and Auc/t0.5 ratio were significantly more (P less than 0.01) in RC group. Since clofazimine reduced rifampicin absorption, the difference in Ka and tp became more significant in the post-regimen phase (P less than 0.01).

Effect of probenecid on serum rifampicin levels.

Serum Rifampicin levels were determined by a microbiological assay using Staphylococcus aureus in 22 cases of leprosy after administering the drug with and without probenecid. Most of the patients showed higher serum rifampicin levels when probenecid was given along with rifampicin. Six patients showed statistically significant increase in the serum levels of the drug when given in the dose of 300 mg along with 1 g of probenecid one hour before breakfast and these levels were comparable with those obtained following administration of 450 mg of rifampicin alone two hours after breakfast. Thus administration of probenecid preceding rifampicin may be employed to reduce cost of drug as well as hepatotoxicity in patients requiring rifampicin for long duration.

Estudio de biodisponibilidad en dos preparaciones distintas de rifampicina / Bioavailability of 2 different rifampicin preparations

Blood levels of two different preparations of Rifampicin were determined after a standard dose of 600mg. Three hours later, blood concentrations showed no statistical differences. Six hours later the levels were statiscally significant well above the minimum inhibitory levels for Mycobacterium Tuberculosis. For practical purposes it may be said that no diference in th bioavailability existis between the two drugs studied...

Determination of three main antileprosy drugs and their main metabolites in serum by high-performance liquid chromatography.

The simultaneous analysis of main antileprosy drugs such as 4,4'-diaminodiphenyl sulfone (DDS), clofazimine, rifampicin and their main metabolites in serum was examined by high-performance liquid chromatography using a muBondapak C18 column. When the drugs dissoluted from serum were developed by tetrahydrofuran-0.5% acetic acid (40:60), clofazimine and rifampicins could be analyzed separately. Apart from the mutual separation of water-soluble conjugates of DDS, the individual analysis of DDS, its main liposoluble metabolite and a few related sulfone compounds is possible when the drugs are first developed by acetonitrile-water (20:80). By the use of tetrahydrofuran-water (50:50) containing PIC B-5, the rapid measurement of clofazimine isolated from the other compounds is also possible.