[Parmentier hygiene and public health]

The legend about Parmentier is quite reductive when it limits his activity to the promotion of potato. This military pharmacist intended mainly to make science serve human being, whatever could be his various activities. Actor of the foundation of food chemistry, reorganizer of military pharmacy, he has always been highly concerned with hygiene and public health. He then studied the quality of water, particularly in the case of river Seine, or the purity of air, especially in hospitals. The affair of Dunkerque exhumations or that of cesspools, or the utilisation of human excrements in agriculture were parts of the occurrences for which he had the opportunity to find a scientific approach allowing to solve the difficult questions that were asked to him, for the best benefit of public health. The exhaustive study he published in "Bulletin de pharmacie" for the conservation of meat shows that he did not ignore anything about freezing of food in order to preserve it. It is necessary not to forget the important role he played, as soon as he were informed of Jenner's discovery, for the diffusion of vaccination in France. It is simply astounding to observe how modern were the questions he solved and how intense was his spirit of dedication to the public good, when exerting his functions in "Comité de Salubrité de la Seine" or "Conseil de Santé des Armées", as well as outside these prestigious institutions.

[Substituted cyclodextrins: an example of biomimetic catalyzers]

Among all molecules used to develop biomimetic catalysts, cyclodextrins are extremely attractive compounds. These oligosaccharides can form inclusion complexes with various organic substrates and in particular with organophosphorus poisons, which are widely used as chemical weapons and insecticides. Soman, a frightening neurotoxic agent, once "trapped" in the internal cavity of beta-cyclodextrin can moreover undergo the nucleophilic attack of an oligosaccharide hydroxyl group, miming the first step of the enzymatic process. Selective substitution of beta-cyclodextrin by a 2-iodosobenzoic acid derivative has enabled effective synthesis of scavangers against organophosphorus compounds. Hydrolysis trials were carried out with paraoxon, as an organophosphorus model. The OP-hydrolyzing activity could reach more than two order of magnitude compared with free 2-iodosobenzoïc acid. Nevertheless, hydrolysis of paraoxon showed saturation kinetics. Although the activity was strongly dependent on the relative position of the reactive group, these results showed the interest of a strategy, resulting in the "trapping" of the organophosphorus substrate in the internal cavity of the oligosaccharide in order to maintain it near the catalytic function.

Les catalyseurs porphyriniques : un outil pour la préparation de modèles de métabolites

The porphyrin complexes of manganese catalysts are biomimetic catalysts whose structural analogy with the active site of cytochrome P-450 enzymes can be used to obtain synthetic models of therapeutic agent metabolites. Mn(TDCOO)Cl, a second generation porphyrin, has proven robust enout to be used for scaled-up production in the presence of hydrogen peroxide and imidazole. For this purpose, an improvement in substrate oxidation was obtained by adjunction of formic acid to the reaction medium which preserved the cocatalyst and the catalyst. It was shown that addition of acid played an active role in the oxidation process. After this optimization, the system was used to oxidate the two enantiomers of methyloctalone, an essential chiral intermediate in the synthesis of terpenoids and steroids. The efficacy of this biomimetic method for the preparation of large amounts of oxidized chiral synthons was better than obtained with biological ex vivo pathways.

Aminoglutethimide included in nanocapsules suspension: comparison of GC–MS and HPLC methods for control

Gas chromatography-mass spectrometry (GC-MS) and high performance liquid chromatography (HPLC) offer highly efficient and potentially sensitive separation and detection techniques. This work describes the quantification of aminoglutethimide (AG) in nanocapsules suspension with both techniques. The analysis of different lots containing known concentrations of drug (1, 2, 3 and 4 mg ml(-1)) were used to investigate the quantitative capabilities of both chromatographic techniques. Both chromatographic methods were successful and on an analytical point of view the validations of aminoglutethimide dosing were suitable in both cases. In routine, the determination of the quality of nanocapsules suspension could be preferentially evaluated by difference between total AG concentration in suspension (evaluated by direct HPLC measure of the suspension diluted in acetonitrile) and free AG concentration (evaluated by direct HPLC measure of simple dilution of the supernatant).

Effects of encapsulation of primidone on its oxidative metabolism in rats

The aim of this study was to evaluate the influence of primidone (PRM) nanoencapsulation on its metabolism. Suspensions of PRM powder and PRM-loaded poly-epsilon-caprolactone nanocapsules were administered orally in the same way to rats. Primidone-loaded poly-epsilon-caprolactone nanocapsules were prepared according to the interfacial deposition technique. Free PRM suspensions were obtained by addition of PRM powder to a suspension of 0.212% carboxymethylcellulose CMC 12H in water. The dose was 20 mg/kg, n = 6, for each experiment. Urinary and faecal levels of PRM and of its three major metabolites, phenylethylmalonamide (PEMA), phenobarbital (PB), and p-hydroxyphenobarbital (p-HO-PB), were determined. Concentrations were evaluated by high-performance liquid chromatography (HPLC) according to a validated analytical method. After PRM nanocapsule administration, non-metabolised PRM urinary levels were increased compared to those observed after administration of a suspension of primidone powder (43.7+/-8.8% after PRM-loaded nanocapsule and 37.7+/-8.1% after free PRM administration). For phenylethylmalonamide, no difference was observed in urinary excretion in the two cases. For two of the oxidised metabolites, PB and p-HO-PB, excretion was delayed and shortened. The amount of these oxidised metabolites was lowered from 0.95% after free PRM administration to 0.25% after PRM-loaded nanocapsule administration. No difference was noted in non-metabolised primidone excretion in faeces. These results suggest that primidone-loaded nanocapsules could be used as a vehicle for oral primidone administration in order to minimise the phenobarbital metabolic pathway.

[A short letter revealing the concerns of XVIIIth century apothecaries]

A letter from Demoret, Paris apothecary, to Le Chandelier, Rouen apothecary, evoked the defense of the interests of the profession, the practice of the profession and the family life of apothecaries of the XVIIIth Century. The important question of the examinations of hospital apothecaries, called "gagnants-maîtrises", and the question of soft drinks makers sailing syrups were treated. The trouble caused by the public display of theriaca, the illness of an assistant or the inspection by guards and physicians were described. Drug supply by colleagues from another town was pointed out. Finally the family life showed the hardness of the period and the way the sons of an apothecary were educated. The interest of this text is that it gives the opinion of an individual concerning general matters.

[The new 1995 code of ethics compared to the 1508 statutes of apothecaries from Rouen]

The new 1995 code of ethics contains many articles which closely correspond to articles which were included in the 1508 statutes of apothecaries from Rouen. Some examples are given and show that human beings have to be protected from abuses by the same kind of barriers at the end of the 20th century as they had to be in 1508.

[The 1791 project of rules for pharmacy: an attempt, in Rouen, to find an alternative to apothecaries' communities]

In 1791, the apothecaries' communities were suppressed, but two weeks later the ancients rules were restored. Nevertheless this situation was provisional and it was time to think of new regulations. The apothecaries from Rouen redacted a project inspired by both the 1508 regulations and the Royal 1777 declaration creating the College of Pharmacy in Paris. This project does not seem to have received any application. The statutes of the free society of pharmacists of Rouen created in 1802, did not refer to this project.

[The Gallot affair, or the long history of drugs from the Flanders army]

After the war, for the Austrian succession, the drugs which had been prepared for the french army, operating in Flanders, were sold to a grocer from Rouen, Pierre Gallot. He tried during twenty years to sail these drugs, which were getting older and older. The apothecaries' community members made their best to avoid the dispensation of these faulty drugs by an unqualified person. These periods 1750, 1756-1758 and 1770-1771 were especially rich in incidents. Many documents allow to follow the evolution of the conflict. Finally the grocer was condamned.

[Eau de mille-fleurs which made Kings' cat dance]

King Louis XV had a cat and some of his courtiers forced it to dance using eau de mille-fleurs (thousand flowers water). This name was given both to cow urine and to the distilled water obtained from cow dung. In this case, the medicine used was George Bate's eau de mille-fleurs, which contained alcohol.

[Some steps of the history of Pharmacy in Rouen]

The community of apothecaries was created in Rouen, in 1508, and its statutes were completed in 1588. The Le Chandelier family was a good example of a dynasty of apothecaries. Precise information on the way of life of XVIIth century apothecaries was given by Jacob Congnard's post mortem inventory. This document revealed also the part played by the apothecaries in foreign trade. The contribution to science was represented by Nicolas Lemery and Francois-Antoine-Henri Descroizilles. After the modifications of the rules by the law of Germinal an XI, the Preparatory School of Medicine and Pharmacy was created in 1841, but it became a faculty, only in 1966.

[Clarification on publications concerning the synthesis of acetylsalicylic acid]

Charles Frédéric Gerhardt (1816-1856) mentioned in his Traité de chimie Organique (1854) a publication, in French (realized in 1852 but published in 1853) entitled "Researches on anhydrous organic acids" in which, was reported the reaction of sodium salicylate with acetyl chloride. He thought that the reaction product was an acid anhydride, but obtained really crude acetylsalicylic acid. Later on, but also in 1853, a publication in german, by the same author related the same experiments. Surprisingly only the second publication has been mentioned in most of the historical studies on the subject. Acetyl salicylic acid was identified and synthesised in 1859 by von Gilm by another method and the product obtained by Gerhardt was identified to it in 1869.

[Wholesale dealers and apothecaries in Rouen]

Wholesale dealers are merchants who sell only great amounts of drugs. Since the XVIth century, the conditions under which they practiced were governed by apothecaries' statutes. The control of drugs, which was performed by apothecaries, was often contested by wholesale dealers. After many proceedings, the court decided in favor of apothecaries.

[Aspirin throughout the ages: a historical review]

Even at the beginning of the next millennium, aspirin will still offer surprises. Its relatively young pharmacological history compares with the early use of salicylate-containing plants since antiquity. The Assyrians and the Egyptians were aware of the analgesic effects of a decoction of myrtle or willow leaves for joint pains. Hippocrates recommended chewing willow leaves for analgesia in childbirth and the Reverend Edward Stones is acknowledged as the first person to scientifically define the beneficial antipyretic effects of willow bark. At the beginning of the 19th century salicin was extracted from willow bark and purified. Although a French chemist, Charles Gerhardt, was the first to synthesize aspirin in a crude form, the compound was ignored, and later studied by Felix Hoffmann. He reportedly tested the rediscovered agent on himself and on his father, who suffered from chronic arthritis--a legend was born and Bayer Laboratories rose to the heights of the pharmacological world. First used for its potent analgesic, antipyretic and anti-inflammatory properties, aspirin was successfully used as an antithrombotic agent. Sir John Vane elucidated aspirin's active mechanism as an inhibitor of prostaglandin synthetase and received the Nobel Price in Medicine for this work in 1982. Two isoform of cyclooxygenase (COX-1 and COX-2) have now been identified, each possessing similar activities, but differing in characteristic tissue expression. The cox enzyme is now a target of drug interventions against the inflammatory process. After two centuries of evaluation, aspirin remains topical, and new therapeutic indications are increasingly being studied.

[Latin and the training of apothecaries in France]

Reading pharmacopoeias and prescriptions, redacted in this degenerated latin which was the language of science, required a sufficient knowledge of that language. A study of the statutes of apothecaries' communities, is a good method to evaluate the role of latin in the training of apothecaries. These statutes could be divided into four groups: statutes redacted in latin, statutes redacted in french, but mentioning that latin was used for the examinations, statutes which mention a control of the capacity of the candidates to understand latin, statutes which do not mention latin. Some examples show the reality of latin knowledge. During the XVIth century, apothecaries used to travel to foreign counties in order to improve their knowledge. They had not to learn the language of the country, because masters and students used to speak latin. Young Balthazar Hummel, from Basel, went to Montpellier, in the house of the apothecary, Laurent Catelan, and never had to learn french, because he used only latin. During the XVIIIth century, apothecaries of Hôtel-Dieu, a hospital in Rouen, were reunited after a competitive examination. On friday May 15th 1722, two candidates, Pierre Lechandelier and Michel Delaisement, had to answer in latin to the questions of the members of the jury. One of them, Lechandelier said that be was not able to do so in latin. He was then told that it was the rule and that he was not allowed to continue the examination. Delaisement answered to the questions in very good latin and became the apothecary of the hospital. His study shows that latin knowledge was required for apothecaries, even if differences appeared between the various french towns. So far as pharmacopoeias were concerned, an evolution took place at the end of the XVIIth century, Charas and Lémery wrote their famous books in french. But until 1818, the official pharmakopoeias were redacted in latin, which was still required for the training of apothecaries.

Competition between the beta-hydroxylation of a primary and a tertiary carbon atom in rats

In order to study the effect of steric hindrance on competition between two kinds of beta-hydroxylation, a compound bearing on a pyrimidinetrione nucleus both a branched side chain with a tertiary carbon atom in position beta (isobutyl group) and a linear side chain (ethyl group), was selected and administered to rats. Urine and faeces were collected and extracted. Hydroxymetabolites and their derivatives were isolated and then identified. The beta-hydroxylation of the linear chain was more important than the beta-hydroxylation of the branched chain. Steric hindrance plays a decisive role in this regioselectivity.

University education of medicinal chemists: comparison of eight countries

Medicinal chemists are mainly taught in faculties or schools of pharmacy and are available for employment. Yet major pharmaceutical research companies seek organic chemists, rather than medicinal chemists, for new drug discovery. This apparent contradiction led the Medicinal Chemistry Section of IUPAC to send a questionnaire regarding postgraduate academic education for medicinal chemists to the faculties or schools of pharmacy in eight countries, namely, France, Germany, Italy, Japan, Spain, Switzerland, UK and USA. The questionnaire aimed to elicit information about postgraduate medicinal chemistry students, their courses and training, and the occupations taken up after graduation. The replies representing 109 medicinal chemistry departments or sections have been analysed and the results are presented to provide a data base on modern medicinal chemistry curricula for comparative purposes. The information should help guide discussion of the optimum paths to be followed by students in preparation for their careers. The evidence suggests that academic training of medicinal chemists equips them to enter a wide range of occupations, many of which are in industry.

Primidone-loaded poly-epsilon-caprolactone nanocapsules: incorporation efficiency and in vitro release profiles

This paper describes the preparation of primidone-loaded poly-epsilon-caprolactone nanocapsules according to the interfacial deposition technique. The colloidal suspension obtained showed a monomodal size distribution with a mean diameter ranging from 308 to 352 nm. By adjusting the process parameters, the encapsulation efficiency was about 74% with good reproducibility. Primidone release from the nanocapsules was found to be slower as compared to the oily control solution despite an important burst-effect. The release profile was not influenced by the pH of the release medium.

Simultaneous determination of primidone and its three major metabolites in rat urine by high-performance liquid chromatography using solid-phase extraction

A new high-performance liquid chromatographic method for simultaneous determination of primidone (PRM) and of its three major metabolites, phenobarbital (PB), p-hydroxyphenobarbital (p-HO-PB) and phenylethylmalonamide (PEMA), in rat urine, was developed. After acid hydrolysis, these compounds were extracted from urine by means of a Bond Elut Certify LRC column with good clean-up. The extracts were chromatographed on a C18 reversed-phase column using isocratic elution at 40 degrees C, with UV detection at 227 nm. The limit of detection was 0.5 mg/ml for the four compounds. Good linearity (r2>0.99) was observed within the calibration ranges studied: 37.4-299.3 microg/ml for PRM, 26.4-211.2 microg/ml for PB, 12.5-100.2 microg/ml for p-HO-PB and 12.1-97.0 microg/ml for PEMA. Repeatability was in the range 3.1-6.8%. This method constitutes a useful tool for studies on the influence of various parameters on primidone metabolism.

Entrapment efficiency and initial release of phenylbutazone from nanocapsules prepared from different polyesters

Several formulations of poly(epsilon-caprolactone) (PCL), poly(lactic acid) (PLA), and poly(lactic-co-glycolic acid) (PLGA) nanocapsules containing phenylbutazone were prepared according to the interfacial deposition technique. These formulations differed in the type of polymer used to form the shell of the nanocapsules. Analysis of particle size distribution and encapsulation efficiency of the nanocapsules revealed that the type and molecular weight of polyester used were the main factors influencing these properties. PLA had the highest encapsulation efficiency with the best reproducibility. From in vitro release studies, a small amount of drug release was observed at pH 7.4. However, in the gastric medium, an important burst effect occurred and was highest with the PLGAs and lowest with PCL, suggesting that drug release from these systems is affected by the type of polymer and the environmental conditions. The two formulations of phenylbutazone-loaded nanocapsules should be evaluated based on PCL and PLA in vivo in order to determine to what extent they are able to reduce the local side effects of this drug.

Determination of pyrazinamide and its main metabolites in rat urine by high-performance liquid chromatography

A new high-performance liquid chromatograhic procedure for simultaneous determination of pyrazinamide (PZA) and its three metabolites 5-hydroxypyrazinamide (5-OH-PZA), pyrazinoic acid (PA), and 5-hydroxypyrazinoic acid (5-OH-PA), in rat urine was developed. 5-OH-PZA and 5-OH-PA standards were obtained by enzymatic synthesis (xanthine oxidase) and checked by HPLC and GC-MS. Chromatographic separation was achieved in 0.01 M KH2PO4 (pH 5.2), circulating at 0.9 ml/min, on a C18 silica column, at 22 degrees C. The limits of detection were 300 microg/l for PZA, 125 microg/l for PA, 90 microg/l for 5-OH-PZA and 70 microg/l for 5-OH-PA. Good linearity (r2>0.99) was observed within the calibration ranges studied: 0.375-7.50 mg/l for PZA, 0.416-3.33 mg/l for PA, 0.830-6.64 mg/l for 5-OH-PZA and 2.83-22.6 mg/l for 5-OHPA. Accuracy was always lower than +/- 10.8%. Precision was in the range 0.33-5.7%. The method will constitute a useful tool for studies on the influence of drug interactions in tuberculosis treatment.

Phenobarbital metabolism by hepatocytes isolated from rat

In order to test the validity of the use of hepatocytes as an alternative to studies of metabolism in live animals, phenobarbital (PB) was applied at 37 degrees C to isolated rat hepatocytes, which had been previously induced by PB. The metabolites were extracted by ethyl acetate, at various pH, and identified and evaluated by GC-MS. PB was not metabolized to p-hydroxyphenobarbital as is usually the case in living animals, but it was transformed into sulphoconjugated 2-phenyl-gamma-butyrolactone. This pathway, beta-hydroxylation of the ethyl side chain followed by lactonization, previously described as a secondary metabolic pathway occurring during intoxications, was here the only observed biodegradation. These results show that it is not possible to use hepatocytes as an alternative to live animals.

GC-MS determination of phenobarbitone entrapped in poly-epsilon-caprolactone nanocapsules

In order to evaluate the concentration of a hydrophilic drug, phenobarbitone, in a suspension of poly-epsilon-caprolactone nanocapsules, a gas chromatographic-mass spectrometric procedure, performed after methylation of the drug, was developed and validated. Free phenobarbitone (in solution in the liquid phase), released phenobarbitone (after opening the nanocapsules with ethyl acetate) and total entrapped phenobarbitone (after extraction with methylene chloride), were measured. Experimental results for four lots with various concentrations showed that the highest preparation of entrapped drug (80%) was obtained for a total concentration of 3.64 mg ml-1 in the nanocapsule suspension.

Gas chromatographic-mass spectrometric method for analysis of a pyrimido-s-triazine and some of its metabolites in dog urine

3-Phenylpyrimido-[3,4-a]-s-triazines exhibit antiparasitic, antibacterial and antifungal activity. In order to study the metabolism of these heterocycles, 9,9-diethyl-3-phenyl-6,8-dioxo-2,3,4,5,6,7,8,9-octahydropyrimido[3 ,4-a]-s- triazine (TZ) was administered to dogs. Three potential metabolites were synthesized, and these models were identified and quantified with gas chromatography-mass spectrometry. The heterobicyclic compounds, TZ and its hydroxy derivative, underwent thermal degradation under chromatographic conditions. Dog urine spiked with the model metabolites was extracted, and the substances were quantified. The urine of dogs treated with TZ was studied, and two of the potential metabolites were recovered, identified and quantified.

[Chromic oxidation and synthesis of barbiturate metabolites]

Chromic oxidation using chromium trioxide in acetic medium is presented as a tool for the synthesis of models of metabolites of various barbiturates. When the pyrimidinetrione is monosubstituted in position 5, a hydroxy group is introduced on the ring. For 5,5-disubstituted barbiturates, branched chains are preferentially converted into tertiary alcohols, while ethylenic chains are, according to their substitution, oxidized into ketones or carboxylic acids. Secondary alcohols lead to ketones but an alcohol function can be protected by esterification. Oxidations followed by other transformations and oxidations of related heterocycles are also described.

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.

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.