Metabolic fate of methoxamine and n-isopropylmethoxamine

Bis[(para-methoxy)benzyl] phosphonate prodrugs with improved stability and enhanced cell penetration

A series of substituted bis[(para-methoxy)benzyl] (bisPMB) esters of 1-naphthalenemethylphosphonate (NMPA) were synthesized and evaluated as phosphonate prodrugs. BisPMB NMPA esters (4b and 4c) with significantly improved aqueous stability were identified that also resulted in increased intracellular levels of NMPA following prodrug incubation with primary rat hepatocytes.

Intra-anal and rectal application of l-erythro methoxamine gel increases anal resting pressure in healthy volunteers

Background

This study examined the effect of a single local application of l-erythro methoxamine, an α1-adrenoceptor agonist, on mean anal resting pressure (MARP) and cardiovascular variables in healthy volunteers.

Methods

l-Erythro methoxamine gel was administered in a single-blind manner; 0·3–3 per cent gels were applied perianally (n = 12), 1–3 per cent gels intra-anally (n = 16) and 1 per cent gel rectally (n = 8). MARP, systolic blood pressure, diastolic blood pressure and pulse rate were measured before application and for up to 6 h afterwards. Blood samples were taken to estimate plasma drug levels.

Results

Perianal gel produced no increase in MARP. Intra-anal 1 per cent and 3 per cent gel produced a significant rapid rise in MARP for 4 and 5 h respectively after application (P = 0·012 and P = 0·017 respectively). Rectal 1 per cent gel increased MARP for 2 h after application (P = 0·036). Intra-anal gel resulted in an increase in systolic blood pressure (1 per cent gel at 2 h, P = 0·042; 3 per cent gel at 4 h, P = 0·017). One per cent intra-anal and rectal gels caused a decrease in the pulse rate for 2 h after application (P = 0·012 and P = 0·018 respectively). Six subjects complained of nausea and three of headache after gel application.

Conclusion

Intra-anal and rectal gel produced a sustained rise in MARP with rapid onset in volunteers. This raises the possibility of a therapeutic application for l-erythro methoxamine in patients with passive incontinence and internal anal sphincter dysfunction.

Spectrophotometric determination of methoxamine using cerium(IV) in presence of sodium lauryl sulphate and rhodamine-B

A sensitive spectrophotometric assay has been developed for the determination of methoxamine in pure dosage form and in its pharmaceutical preparations. The method is based on the acidic oxidation of methoxamine with cerium(IV) in the micellar medium of sodium lauryl sulphate at 96 degrees C. The reaction yields a water-soluble purple product which can be quantified spectrophotometrically at 505 nm. The calibration curve was linear between 1.0 and 20 micrograms ml-1 with a limit of detection 0.5 microgram ml-1. The molar absorptivity at 505 nm is 8.3 X 10(3) iota mol-1 cm-1. The method is simple and rapid since the product is measured directly in solution without extraction.

Biotransformation of the sympathomimetic tetraminol in vitro

On incubation with the postmitochondrial fraction of the liver homogenate of rabbits, guinea-pigs, rats, and mice in the presence of NADPH and oxygen, the alpha-sympathomimetic trans-3-(2-hydroxyethylamino)-5,8-dimethoxy-1,2,3,4-tetrahydro-2-n aphthol (Tetraminol, 1) is preferentially O-demethylated in position 8, yielding metabolite 3. In male rats O-demethylation is stronger than in females.

Fungal metabolism of 4-substituted amphetamines

1. rac.-4-Ethoxyamphetamine was incubated with 14 different yeast and fungal microorganisms. 4-Hydroxyamphetamine was the major metabolite; traces of N-acetyl-4-ethoxyamphetamine were also detected. 2. The major fungal (Cunninghamella) metabolite of 4-propoxyamphetamine and 4-benzyloxyamphetamine was 4-hydroxyamphetamine. The major metabolites of 4-methoxyamphetamine were N-acetyl-4-methoxyamphetamine and 4-hydroxyamphetamine. 3. Acetoin derivatives were formed when alkoxyamphetamine substrates were incubated in the presence of various fungi and yeasts. 4. The findings indicate that Cunninghamella echinulata may be a useful microbial model for drug disposition and interaction studies.