Phenelzine in urine: assay and relation to acetylator status

Microbial metabolism of phenelzine and pheniprazine

Phenelzine and pheniprazine were used as substrates for metabolic studies with Cunninghamella echinulata and Mycobacterium smegmatis. Metabolites were identified by means of gas-liquid chromatography and mass spectrometry. 1-Acetyl-2-(2-phenylethyl)-hydrazine and 1-acetyl-2-(1-methyl-2-phenylethyl)hydrazine were the major products of C. echinulata metabolism of phenelzine and pheniprazine, respectively. In addition, M. smegmatis produced a second metabolite from each substrate; these metabolites were unequivocally identified as N-acetylphenylethylamine and N-acetylamphetamine from phenelzine and pheniprazine, respectively.

Analysis of the antidepressant phenelzine in brain tissue and urine using electron-capture gas chromatography

A novel gas chromatographic method for the analysis of the antidepressant phenelzine has been developed. The procedure involves extraction with a liquid ion-pairing compound, back-extraction with HCl, basification, and derivatization with pentafluorobenzoyl chloride. The dipentafluorobenzoyl derivative (structure confirmed by mass spectrometry) is separated and analyzed on a gas chromatograph equipped with a fused silica capillary column and an electron-capture detector. The procedure has been utilized for quantitation of phenelzine in brain of phenelzine-treated rats and in urine from human subjects receiving phenelzine.

Survey of the human acetylator polymorphism in spontaneous disorders

There is ample evidence that the human acetylator phenotypes are associated with drug induced phenomena. It is principally the slow acetylators who exhibit toxic adverse effects because of their relative inability to detoxify the original drug compounds. In rare instances, however, it is the rapid acetylators who are at a disadvantage. In the matter of association of spontaneous disease with either acetylator phenotype, there are two groups of disorders to consider. First, disorders in which carcinogenic amines are known to be an aetiological factor. This is because these amines are substrates for the polymorphic N-acetyltransferase activity and hence there is a possible rational basis for searching for an association. Secondly, other disorders where searches for associations are based more on hunches. In the first group there is a definite statistical association between cancer of the bladder and the slow acetylator phenotype. In prevalence studies the slow phenotype is 39% more associated with bladder cancer than is the rapid phenotype. On the basis of the evidence now available it is not possible to say whether this association is because slow acetylators develop the disease more frequently or whether they survive longer. In the second group the relevant studies show (1) a greatly increased prevalence of slow acetylators in Gilbert's disease; (2) a confirmed association between the rapid acetylator phenotype and diabetes; (3) a possible association between the rapid acetylator phenotype and breast cancer; (4) a possible association between the slow acetylator phenotype and leprosy in Chinese patients; (5) an earlier age of onset of thyrotoxicosis (Graves' disease) in slow acetylators than in rapid acetylators; (6) no evidence of an association between either phenotype and spontaneous systemic lupus erythematosus.

Hydrazine levels in formulations of hydralazine, isoniazid, and phenelzine over a 2-year period

Hydrazine levels in formulations of hydralazine, isoniazid, and phenelzine have been measured over a 2-year period under ambient conditions and under temperature and humidity stress. Hydralazine tablets are stable under ambient conditions, but the hydrazine level in an injectable formulation increased from 4.5 to 10 micrograms/ml over a 23-month period. Isoniazid tablets are also stable, but hydrazine levels in an elixir and a pyridoxine combination product doubled to 44 micrograms/ml and 19 micrograms/tablet, respectively. Levels in phenelzine tablets appeared to remain constant at approximately 60 micrograms/tablet, with considerable tablet-to-tablet variation.

Determination of phenelzine in human plasma with gas chromatography-mass spectrometry using an isotope labeled internal standard

A quantitative gas chromatographic-mass spectrometric assay was developed for the determination of phenelzine in human plasma. Phenelzine, in aqueous solution or in plasma reacts at room temperature with pentafluorobenzaldehyde to form quantitatively a hydrazone derivative. The derivative has good gas chromatographic characteristics. The assay utilizes selected ion monitoring in a gas chromatographic effluent, the molecular ion generated by electron impact ionization of phenelzine derivative. Phenelzine-d, was synthesized and used as an internal standard. The assay can measure 2 ng/ml of the drug with about 10% precision. The method was used for the determination of steady state levels of phenelzine in the plasma of patients taking a therapeutic dose of the drug.

Determination of the acetylator phenotype and pharmacokinetics of some sulphonamides in man

The pharmacokinetics of sulphamethizole, sulphamethoxazole, sulphadiazine, sulphapyridine and sulphadimidine have been studied in man. Renal clearance values of the metabolite N4-acetylsulphonamide are 6 to 20 times higher than those of the corresponding parent compound. The renal clearance of sulphonamides is dependent on the urine flow. N4-Acetylsulphonamide concentration-time profiles for plasma and urine have been constructed for the sulphonamides. The percentage N4-acetylsulphonamide-time profiles for plasma are excellent tools for establishing the acetylator phenotype, while those constructed from urine samples are less useful. Evidence is obtained that sulphadimidine is metabolically processes by 2 different isoenzymes, while sulphadiazine, sulphapyridine and sulphamethoxazole are processes by 1 acetylating isoenzyme. Sulphamethizole is acetylated to very little extent.

Acetylation of phenelzine

Microsome-free preparations of rodent and human liver were shown to contain N-acetyl transferase from experiments using procainamide as substrate. These preparations then acetylated phenelzine from the quantitative transfer of radiolabeled acetate. This in vitro demonstration of phenelzine acetylation in rodent and human liver was corroborated by the finding of a negative correlation between excretion of phenelzine in urine and sulphadimidine acetylation in 27 patients.