Characterization of a novel diclofenac metabolite in human urine by capillary gas chromatography-negative chemical ionization mass spectrometry.

A sensitive analytical method was developed to characterize diclofenac metabolites in small amounts of body fluids. Desalted and lyophilized urine samples were extracted with supercritical carbon dioxide directly or after acidic hydrolysis. The extracts were derivatized with N-tert.-butyldimethylsilyl-N-methyltrifluoroacetamide. The derivatives were separated by capillary gas chromatography and identified by negative chemical ionization mass spectrometry. Full mass spectra were obtained at a level of 1.10(-9) g/ml. With direct extraction, the metabolites could be analysed in one step as open-chained acids and as (cyclic) oxindoles. By acidic hydrolysis the conjugates were transformed to the oxindoles. With both methods, a new main metabolite, [2-[2,6-dichloro-4-hydroxy-3-methoxyphenyl)amino]phenyl]acetic acid, was identified The mechanism of its formation is discussed.

Strategies in the design of peptidoleukotriene antagonists.

The research of the last two decades in the field of SRS-A and peptidoleukotriene (pLT) antagonists has provided information for the design of potent pLT antagonists, which share some or all of the following structural elements: (1) a lipophilic anchor, which fits into the lipophilic pocket of the LTD4 receptor; (2) a central lipophilic unit mimicking the tetraene system of LTD4; (3) one or two acidic groups, as mimics of the cysteinyl-glycine unit and/or the carboxylic group in the eicosanoid backbone of LTD4; (4) spacers connecting these elements. Potent pLT antagonists lacking a second polar binding group compensate by stronger interaction in other regions of the receptor. Identification of pLT antagonists is based on lead optimisation, preparation of pLT analogs and on the knowledge of the pLT receptor.

Pharmacological properties of five diclofenac metabolites identified in human plasma.

Five metabolites of diclofenac sodium (Voltarol) have been identified in human plasma. All five metabolites were more than 50 times less potent than diclofenac in inhibiting PGE2 production in zymosan-stimulated mouse macrophages and LTC4 synthesis was not inhibited in these cells. Anti-inflammatory activity (adjuvant arthritis and carragheenan-induced paw oedema in rats) and analgesic activity (phenyl-p-benzoquinone writhing, mouse) of the metabolites were at least 10 times lower when compared to diclofenac. There was a good correlation between in vitro PGE2 inhibition and in vivo activities for diclofenac and its metabolites indicating that inhibition of prostaglandin synthesis is a major mechanism responsible for their pharmacological actions.

Synthesis and quantitative structure-activity relationships of diclofenac analogues.

The synthesis of a series of 2-anilinophenylacetic acids, close analogues of diclofenac, is described. These compounds were tested in two models used for evaluating the activity of nonsteroidal antiinflammatory drugs (NSAID's), inhibition of cyclooxygenase enzyme activity in vitro, and adjuvant-induced arthritis (AdA) in rats. Statistically significant correlations were found between the inhibitory activities of the compounds in these two models, indicating that cyclooxygenase inhibition seems to be the underlying mechanism for the antiinflammatory activity of these compounds. Quantitative structure-activity relationship (QSAR) analysis revealed that the crucial parameters for activity in both models were the lipophilicity and the angle of twist between the two phenyl rings. Optimal activities were associated with halogen or alkyl substituents in both ortho positions of the anilino ring. Compounds with OH groups in addition to two ortho substituents or compounds with only one or no ortho substituents were less active.

The history of diclofenac.

The purpose in developing diclofenac sodium was to synthesize a nonsteroidal anti-inflammatory drug with high activity and outstanding tolerability. Factors considered were drug transport through biologic membranes, the atomic and spatial structure of the molecule, and the electronic structure. Based on analysis of other nonsteroidal anti-inflammatory drugs, it was postulated that an effective antirheumatic agent should have the following characteristics: an acidity constant between 4 and 5, a partition coefficient of approximately 10, and two aromatic rings twisted in relation to each other. The result was diclofenac sodium, which has an acidity constant of 4.0 and a partition coefficient of 13.4. The structural elements include a phenylacetic acid group, a secondary amino group, and a phenyl ring containing chlorine atoms, which cause maximum twisting of the ring. Experimental and clinical findings obtained to date have indicated that diclofenac sodium was synthesized on well-founded principles.

Biotransformation of diclofenac sodium (Voltaren) in animals and in man. I. Isolation and identification of principal metabolites.

1. The anti-inflammatory agent diclofenac sodium (o-[(2,6-dichlorophenyl)amino]phenylacetic acid sodium salt) is extensively metabolized by rat, dog, baboon and man. The main metabolites were isolated from the urine of all species and from the bile of rat and dog and identified by spectroscopy. 2. Metabolism involves direct conjugation of the unchanged drug, or oxidation of the aromatic rings usually followed by conjugation. Sites of oxidation are either position 3' or 4' of the dichlorophenyl ring or, alternatively, position 5 of the phenyl ring attached to the acetic acid moiety. 3. In the urine of rat, baboon and man conjugates of the hydroxylated metabolites predominate, but the major metabolite in dog urine is the taurine conjugate of unchanged diclofenac. 4. In the bile of rat and dog, the main metabolite is the ester glucuroniade of unchanged diclofenac.

The chemistry of diclofenac sodium (Voltarol).

The study of phenylbutazone and of the major anti-inflammatory agents which followed a decade later provided target criteria for a research project aimed at the synthesis of a new anti-inflammatory agent with superior activity and tolerability. Diclofenac fulfils the steric and physicochemical criteria, and the absence of a heterocyclic ring from its chemical structure may have a beneficial influence on its tolerability.

Pharmacological properties of diclofenac sodium and its metabolites.

Diclofenac sodium (Voltaren) is a non-steroid anti-inflammatory agent of a new chemical structure, which is animal experiments shows a high degree of anti inflammatory, analgesic, and antipyretic activity in various pharmacological models. It inhibits prostaglandin biosynthesis in vitro and in vivo, and this inhibitory effect at least partly explains the mechanism of action of the preparation. In animal experiments diclofenac sodium is characterised by a broad therapeutic range. Also, its gastrointestinal tolerability is better than that of other highly effective non-steroid anti-inflammatory agents. Two of the metabolites produced during the biotransformation of diclofenac sodium in man are also biologically active. The activity of these two metabolites, however, is very much weaker than that of unchanged diclofenac sodium and is comparable to that of phenylbutazone.