Pharmacokinetics of pyrazinamide and its metabolites in patients with hepatic cirrhotic insufficiency

The pharmacokinetics of pyrazinamide (Pirilène) and its metabolites are evaluated in ten subjects with hepatic insufficiency, after an oral dose of 19.3 +/- 0.6 mg.kg-1 and the results are compared to those of a group of nine healthy subjects (control group). The results exhibit a marked reduction of the pyrazinamide total clearance (0.48 vs 0.84 ml.min-1.kg-1) and an increase in half-life from 9.19 h to 15.07 h in the patients group. The area under the curve of pyrazinoic acid (the main metabolite) is increased from 97 to 280 mg.h.l-1 with a half-life twice as much as that of the control group. The hepatic insufficiency entails a marked reduction of the common posology as well as a closer survey of the biologic hepatic parameters and of uric acid the renal elimination of which is inhibited by pyrazinoic acid.

Pharmacokinetics of pyrazinamide and its metabolites in healthy subjects

The plasma and urine pharmacokinetic parameters of pyrazinamide and of its metabolites (pyrazinoic acid, 5-hydroxy-pyrazinamide, 5-hydroxy-pyrazinoic acid and pyrazinuric acid) have been studied after a single oral dose of pyrazinamide 27 mg.kg-1 in 9 healthy subjects. Pyrazinamide was rapidly absorbed (tmax less than or equal to 1 h) and showed a short distribution phase followed by an elimination phase of t1/2 beta = 9.6 h. The close similarity of the apparent elimination rates of the metabolites led to a second trial of a single oral dose of pyrazinoic acid to evaluate the formation and elimination stages. The limiting factor was found to be the activity of a microsomal deamidase (pyrazinoic acid formation from pyrazinamide and 5-hydroxy-pyrazinoic acid formation from 5-hydroxy-pyrazinamide). In contrast, oxidation by xanthine oxidase occurred very rapidly (5-hydroxy-pyrazinamide formation and pyrazinoic acid catabolism to 5-hydroxy-pyrazinoic acid).

Haemodialysis of pyrazinamide in uraemic patients

The pharmacokinetics of PZA during haemodialysis were determined in 6 patients with chronic renal impairment after a single oral dose of 25.7 (1.9) mg.kg-1. The dialysis clearance of PZA and of its metabolites were: pyrazinamide 132 ml.min-1; pyrazinoic acid 121 ml.min-1; 5-hydroxy-pyrazinamide 107 ml.min-1; 5-hydroxy-pyrazinoic acid 118 ml.min-1. The average amount extracted during a dialysis session of 4.1 h was 926 mg after an oral dose of 1700 mg. The high dialysability shows that PZA can properly be administered at the end of each dialysis session in the usual dose of 25 to 30 mg.kg-1.

Sugar Utilization and Acid Production by Free and Entrapped Cells of Streptococcus salivarius subsp. thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, and Lactococcus lactis subsp. lactis in a Whey Permeate Medium

Cells of Streptococcus salivarius subsp. thermophilus and Lactococcus lactis subsp. lactis entrapped in k -carrageenan-locust bean gum gel performed similarly to free cells in the conversion of lactose to lactic acid. Bead diameter influenced the fermentation rate. Cells entrapped in smaller beads (0.5 to 1.0 mm) showed higher release rates, higher lactose, glucose, and formic acid utilization, higher galactose accumulation, and higher lactic acid production than did cells entrapped in larger beads (1.0 to 2.0 mm). Values for smaller beads were comparable with those for free cells. Immobilization affected the fermentation rate of lactic acid bacteria, especially Lactobacillus delbrueckii subsp. bulgaricus. Entrapped cells of L. delbrueckii subsp. bulgaricus demonstrated a lower lactic acid production than did free cells in batch fermentation. The kinetics of the production of formic and pyruvic acids by L. lactis subsp. lactis and S. salivarius subsp. thermophilus are presented.

Interaction between allopurinol and pyrazinamide

Pyrazinamide (PZA) is increasingly used with isoniazid and rifampicin, in short-course antituberculous chemotherapy in service programme conditions. Complicating arthralgias occur due to hyperuricaemia induced by the inhibition of renal tubular secretion of uric acid by pyrazinoic acid, the main PZA metabolite. Allopurinol (Al), a hypouricaemic agent, provides no substantial clinical improvement. Pharmacokinetics of PZA and its metabolites were studied in six healthy volunteers, in a cross-over design, after a single oral dose of PZA alone and, in a second trial, after the same dose together with Al. Plasma and urinary concentrations were measured by high pressure liquid chromatography with a column of cation exchange resin. Analysis of the pharmacokinetic parameters showed that Al induced marked changes in levels of PZA metabolites and accumulation of pyrazinoic acid. Despite decreasing uric acid synthesis, allopurinol increased plasma concentrations of pyrazinoic acid, which is directly responsible for the inhibition of renal urate secretion. Other drugs, which do not involve xanthine oxidase inhibition, should be used in the treatment of this side effect of chemotherapy.

Interaction between allopurinol and pyrazinamide

Pyrazinamide (PZA) is increasingly used with isoniazid and rifampicin, in short-course antituberculous chemotherapy in service programme conditions. Complicating arthralgias occur due to hyperuricaemia induced by the inhibition of renal tubular secretion of uric acid by pyrazinoic acid, the main PZA metabolite. Allopurinol (Al), a hypouricaemic agent, provides no substantial clinical improvement. Pharmacokinetics of PZA and its metabolites were studied in six healthy volunteers, in a cross-over design, after a single oral dose of PZA alone and, in a second trial, after the same dose together with Al. Plasma and urinary concentrations were measured by high pressure liquid chromatography with a column of cation exchange resin. Analysis of the pharmacokinetic parameters showed that Al induced marked changes in levels of PZA metabolites and accumulation of pyrazinoic acid. Despite decreasing uric acid synthesis, allopurinol increased plasma concentrations of pyrazinoic acid, which is directly responsible for the inhibition of renal urate secretion. Other drugs, which do not involve xanthine oxidase inhibition, should be used in the treatment of this side effect of chemotherapy.

Inflammatory lesions of peripheral nerve in a patient with human T-lymphotropic virus type I--associated myelopathy

In a patient with tropical spastic paraparesis associated with a positive titer for human T-lymphotropic virus type I, electrophysiological study detected a mixed, axonal and demyelinating, multifocal neuropathy. Perineural and perivascular infiltrates, moderate axon loss, wallerian degeneration, and demyelinating lesions of isolated fibers were present in the nerve biopsy specimen. These inflammatory lesions resembled those found in the central nervous system of patients with tropical spastic paraparesis.

Cryptosporidium oocysts in immunocompetent children: epidemiologic investigations in the day-care centers of Poitiers, France

The recent discovery of self-resolving Cryptosporidium infection in immunocompetent patients has aroused growing interest in this parasite, which has thus far been known to affect mainly immunodeficient individuals. Following the hospitalization of two children attending the same day-care center in February 1986 Cryptosporidium oocysts were found in the stools of one of them. This led to an epidemiological investigation to assess the frequency of Cryptosporidium oocysts in the stools of children attending the 7 day-care centers in the city of Poitiers, France. Testing for Cryptosporidium oocysts was performed on formalinized stools, after smear staining by the modified Ziehl-Neelsen procedure. Each positive stool was also submitted to virological and bacteriological examination. Stool specimens from 235 children were studied: 9 (3.8%) of them had Cryptosporidium oocysts in their stools. Four of the children had diarrhea, and 5 (2.2%) were asymptomatic. The existence of healthy carriers should lead to caution in the interpretation of stool parasitology.

[Microdetermination of pyrazinamide and its metabolites (pyrazinoic acid, 5-hydroxypyrazinoic acid, 5-hydroxypyrazinamide and pyrazinuric acid) in plasma and urine with liquid chromatography]

The method reported here for determining pyrazinamide and its metabolites (2-pyrazinoic acid, 5-hydroxypyrazinamide, 5-hydroxypyrazinoic acid and pyrazinuric acid) consists of diluting urine or acid deproteinisation of serum followed by chromatography on a cation-exchange column. The column length and the detection system (ultraviolet or fluorimetry) allow for a very good separation of the different compounds; the sensitivity of the method makes it suitable for pharmacokinetic studies.

Simultaneous radioimmunoassay of progesterone, androst-4-enedione, pregnenolone, dehydroepiandrosterone and 17-hydroxyprogesterone in specific regions of human brain

Simultaneous determination of progesterone, androst-4-enedione, pregnenolone, dehydroepiandrosterone (DHEA) and 17-hydroxyprogesterone has been developed for human cerebral tissue. Before immunoassay, steroids were separated on a Celite column with propylene glycol as stationary phase with hexane containing increasing proportions of dichloromethane as mobile phase. This system allowed separation of steroids of similar polarity, especially of pregnenolone and progesterone. The brain regions studied cortex (prefrontal, parietal and temporal), cerebellum and corpus callosum, were obtained after autopsy from 9 women and 1 man between 76 and 93 years of age. Steroids were found in all regions. The overall concentrations expressed in nmol/kg of tissue were: 10.1, 7.6, 120.7, 19.6 and 10.4 respectively, for progesterone, androst-4-enedione, pregnenolone, dehydroepiandrosterone and 17-hydroxyprogesterone, corresponding to 7.3, 4.9, 74, 6.5 and 9.2 times the plasma levels. These very high concentrations, not previously described in human brain tissue, pose the question of the existence of local biosynthetic pathways independent of the peripheral endocrine gland system as well as that of progressive accumulation of steroids over a lifetime. Concentrations of each steroid in each subject varied little among the various brain regions studied, but there was much variation among the subjects with respect to the concentrations of a given steroid.

[Determination of plasma ethambutol with liquid chromatography and ultraviolet spectrophotometry]

The method presented here is based on the ability of ethambutol to give chelates with divalent cationic metals. With copper salts, the chelate presents a characteristic ultraviolet absorbance at 270 nm, making it possible to titrate ethambutol extracted from plasma with chloroform in alkaline medium. The column which was used contained silica (LiChrosorb Si 60, 5 microns) and the mobile phase was a mixture of equal parts of water and acetonitrile, containing copper sulphate and ammonia. The internal standard was a lower homologue of ethambutol with the same chelating ability. The detection limit was 0.15 mg/l. No interference with other antitubercular agents was observed.

Total DNA synthesis and cloning in Escherichia coli of a gene coding for the human growth hormone releasing factor

A DNA containing a sequence coding for the human growth hormone releasing factor (hGRF) has been obtained by enzymatic assembly of chemically synthesized DNA fragments. The synthetic gene consists of a 140 base-pair fragment containing initiation and termination signals for translation and appropriate protruding ends for cloning into a newly constructed plasmid vector (pULB1219). Eleven oligodeoxyribonucleotides, from 14 to 31 bases in length, sharing pairwise stretches of complementary regions of at least 13 bases were prepared by phosphotriester solid-phase synthesis. The DNA sequence was designed to take into account the optimal use of E. coli codons. Oligomers were annealed in one step and assembled by ligation. The DNA fragment of the expected size (140 bp) was recovered and cloned into the pULB1219 vector. The expected sequence was confirmed by DNA sequencing.