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The products of metabolism of norephedrine by 10 000 g fractions of rabbit liver microsomes have been shown to be norephedrine hydroxylamine, l-hydroxy-2-oxo-l-phenylpropane oxime, 1-hydroxy-2-oxo-1-phenylpropane, 1,2-dihydroxy-l-phenylpropane (erythro). N-Oxidation was at least as important as α-C-oxidation. The synthesis and properties of the metabolic products are described.

In vitro incubation of (±)-N-(n-propyl)amphetamine (NPA) with the 12 000 g supernatant fraction of rat liver homogenate resulted in the formation of two N-oxygenated products identified as N-hydroxy-1-phenyl-2-(n-propylamino)propane and N-[(1-methyl-2-phenyl) ethyl]-1-propanimine N-oxide by g.l.c, g.l.c.-m.s. and t.l.c. Amphetamine, phenylacetone, benzyl methyl ketoxime, and a previously unreported metabolite N-(2-hydroxy-n-propyl) amphetamine were also isolated. Increasing the pH of the incubation mixture from 7·4 to 8·4, or in vivo pretreatment of rats with 3-methylcholanthrene caused an increase in the in vitro metabolic N-oxidation of NPA, whereas pretreatment with phenobarbitone or NPA did not. The presence of SKF 525-A in incubation mixtures reduced the amount of C-oxidation and to a lesser degree of N-oxidation. When (+)-NPA or (–)-NPA was used as substrate, C-oxidation was favoured with the former and N-oxidation with the latter.

A direct gas chromatographic method for unstable amino ketones, using a neutral column and moderately alkaline conditions during extraction has been developed. Its application has given a new perspective to the relative importance of the metabolic routes in the complex metabolism of diethylpropion which after oral administration in man is rapid and extensive (only 3–4% of the drug remains unchanged). Mono-N-de-ethylation is the main pathway (about 35% of the dose). N-De-ethylation is more important than carbonyl-reduction, occurring mainly with the unchanged drug (about 20% of the dose). Norephedrine, thought previously to be one of the main metabolites, has been shown to be present only in negligible amounts. About 30% of the dose, which cannot be accounted for as the sum of the amines recovered in urine, is probably metabolized by deamination, followed by oxidation and conjugation to give hippuric acid.

The microsomal N-oxidation of phentermine (Ia) to N-hydroxyphentermine (Ib) and to α,α-dimethyl-α-nitroso-β-phenylethane (Ic) was investigated. Maximum activities were obtained with microsomal (9000 g supernatant and microsomes) fractions of rabbit liver in the presence of an NADPH generating system. Incubation of Ia with hepatic washed microsomes from a phenobarbitone pretreated rabbit increased the formation of Ib and decreased that of Ic but the total amount of N-oxidized metabolites (i.e. Ib + Ic) was not affected. The ratio of the metabolically produced Ic to Ib but not the total amount of N-oxygenated metabolites varied greatly depending of the liver microsomal fractions used in the incubation mixtures of Ia; more Ib was produced from Ia using 9000 g supernatant and conversely, more Ic was formed using the washed microsomes of the same liver. The nitroso compound (Ic) was metabolically reduced to Ib and Ib to Ia by the hepatic 9000 g supernatant and soluble fraction; under the same conditions, washed microsomes had only limited reductive properties towards Ic and Ib. N-Hydroxyphentermine (Ib) was not metabolically oxidized to Ic when incubated with washed microsomes from rabbit liver. The use of known carbon-oxidation inhibitors showed that cytochrome P-450 is not involved in the incorporation of oxygen at the nitrogen centre of Ia. The metabolic characteristics and kinetic behaviour of the microsomal N-oxidation of Ia supported a recently proposed mechanism explaining the independent formation of Ib and Ic from a common precursor resulting from metabolic N-oxidation of Ia.

Significant inter-subject variation in the cumulative urinary excretion of pentazocine, following its oral administration, was observed. Individual variations in the rate of metabolic oxidation of pentazocine are responsible for the variations in the urinary excretion of pentazocine (24 h cumulative). Smoking did not affect the metabolism of the drug. Pharmacokinetic analysis of the urinary excretion rate of pentazocine, using an open three compartment model, indicated that the fractional metabolic clearance is correlated with the cumulative urinary excretion (24 h) of the drug under conditions of acidic urinary pH. A g.l.c. method for the determination of pentazocine in urine is described.

Cathode ray polarography has been used to measure chlorpromazine-N-oxide, N-oxide sulphoxide and chlorpromazine sulphoxide in mixtures. The response was linear when the metabolites were present in the range 10−5 to 5 times 10−8m in aqueous solutions. Reductive polarography of the mixed oxides in solution gave an additive wave from which individual oxides were determined by subtraction. Ultraviolet and Potentiometrie titration methods were used to determine the pKa values of the oxide metabolites of chlorpromazine. The mechanism of the reduction process was investigated using d.c. polarography and preparative micro-electrolysis. Polarographic analysis was applied to the determination of the metabolites after their separation from urine, plasma and microsomal preparations.

The absorption of diethylpropion (DEP I), dimethylpropion (DMP I) and some of their basic metabolites into and passage through the skin was investigated and a comparison of their metabolism following oral and percutaneous administration made. High percentages (60–80%) of DEP I and its metabolites and a small percentage of DMP I and its metabolites were taken up into the skin in less than 2 min—the remaining percentages of the compounds were absorbed into the skin by a first order process. The rate of appearance of the compounds in the blood, which reflects their rate of passage through the skin, did not correlate with their rate of absorption into the skin. More metabolism occurred with all the compounds after their oral administration than after their percutaneous application.

2-Ethylidene-l,5-dimethyl-3,3-diphenylpyrrolidine (II), a cyclic metabonate of methadone was synthesized from methadone (I) and methadone-N-oxide (III). m-Chloroperbenzoic acid was used to oxidatively demethylate I while sulphur dioxide reductively demethylated III to give II. The importance of these syntheses lies in the fact that there is no attack on the asymmetric carbon atom in I or III, thus providing direct methods of obtaining the optical isomers of II.

Amphetamine (I), 1-phenylpropan-2-ol (III), phenylacetone (V), N-hydroxyethylamphetamine (VII), and α-methyl-N-(1′-phenylprop-2′-yl)nitrone (VIII) were obtained as metabolic products from the incubation of ethylamphetamine (II) with fortified male rabbit liver 9000 g supernatant fractions. These metabolites were identified by comparing their t.l.c., g.l.c. and g.l.c.-m.s. behaviour to that of reference compounds. A method for the quantitative analysis of the metabolites in mixtures using g.l.c. techniques is described.

2-Nitroso-1-phenylpropane dimer, a postulated metabolic product of amphetamine, was metabolized by fortified 9000 g supernatants from rabbit liver, mainly by oxidation on the carbon beta to the nitrogen to form a ‘β-hydroxylated nitroso dimer’. The corresponding nitro compound, ketone and alcohol were also products, the latter two but not the former being cofactor dependant. The nitroso compound was not metabolically reduced under the conditions used.

By appropriate choice of trimethylsilylating and trifluoroacetylating reagents and organic solvents for extraction, stable derivatives of aliphatic primary hydroxylamines metabolites, N-hydroxyphentermine, N-hydroxychlorphentermine, N-hydroxymexiletene, N-hydroxy-phenethylamine, N-hydroxyamphetamine, and N-hydroxy-3,4-dimethoxyamphetamine, were obtained and examined by g.l.c. analysis without decomposition and without interference from the parent drug or other metabolic products.

The preparation of levorphanol, dextrorphan and morphine stereoselective adsorbents is described. These adsorbents are used to show that the laevo isomers of morphine, phenazocine and a related compound, and racemorphan and related morphinans have similar configurations; the analgesic activity of the various compounds resides substantially in these laevo isomers.

Some interactions of optically active N-alkyl-NN-dimethylalanine hydrobromide (alkyl betaine) micelles, representing model flexible drug receptors, with simple “drug” molecules, represented by a number of optically active amino-acids, choline derivatives and a dipeptide have been examined. Comparisons of these “drug-receptor” interactions have been made using a refractive index technique and an explanation of the difference in the degree of adsorption of different “drug” molecules at identical micelle surfaces is advanced.

The absorption spectra of the products from the reaction of various hydroxy- and methoxy-phenothiazine derivatives with sulphuric acid are described, and their application to problems of identification of metabolites of promazine and other phenothiazine drugs is discussed. A discussion of the nature of the reaction products is included.

The preparation is described of some 2-hydroxy-2- and 4-alkylmorpholines by ring closure of the corresponding phenacyl hydroxyalkylamines. The influence of structure upon the ring closure reaction is examined and the weak pharmacological action of the title compounds on leptazol convulsions, the autonomic nervous system and in the mouse hot-plate test is discussed in relation to the reversed esters of pethidine.

The addition of various lithium aryl compounds to 1:3-dimethyl-4-piperidone is investigated. Those stereoisomers present as the major proportion of the respective stereoisomeric mixtures are shown to have similar infra-red absorption characteristics which are different from those exhibited by those isomers formed in minor amount. The stereochemistry of addition to 6-membered alicyclic and heterocyclic ketones is discussed; on the basis of these discussions, and the rates of hydrolysis of appropriate esters, the above isomers formed in major amount are allocated the trans (Me/Ar) configuration. The analgesic activities in mice of various stereoisomeric amino-alcohols and esters are given.

A method, involving the use of an analogue computer, is described for determining a quantitative relation between measured urinary pH and the kidney tubular reabsorption of certain drugs under normal conditions of fluctuating urinary pH. The method is based on the use of drug excretion versus time profiles under normal conditions and of absorption, metabolism and excretion rate constants, determined under conditions of controlled urinary pH, e.g. constant acidic pH (

N-Hydroxyamphetamine (Ib) can be extracted from aqueous solutions at neutral pH, but is readily decomposed into syn- and anti-phenylacetone oximes (II) at alkaline pH values. Gas chromatography of Ib is possible, provided the compound does not come into contact with heated metal surfaces. In aqueous media the hydroxylamine can be determined (1) by extraction from the medium with ether and analysis of the ethereal solution by g.l.c.; (2) by separation of the compound on a thin-layer then oxidation of the hydroxylamine spot with ammoniacal silver nitrate to give phenylacetone oximes which may then be determined by g.l.c.; (3) by reduction with lithium aluminium hydride to amphetamine (Ia) followed by g.l.c.; (4) conversion to phenylacetone oximes by shaking at pH 12 in air, extraction of the oximes, followed by g.l.c.; (5) Alternatively, N-hydroxyamphetamine can be determined directly in aqueous solution by polarography provided the measurement is made immediately after the supporting electrolyte, sulphite/NaOH, has been added.

An analogue computer program, incorporating a previously established relation between urinary pH and amphetamine excretion, has been used to predict the quantitative excretion of the drug under normal conditions of fluctuating urinary pH. Under the same conditions, a comparison has been made of computer predicted body levels of amphetamine after administration of the drug in a single solution dose, three divided solution doses, and in various prolonged-release formulations. Advantages of sustained-release preparations are indicated and specifications for a theoretically ideal sustained-release formulation are suggested.

Previously reported data (Beckett & Brookes, 1967) for the excretion of (±)-fenfluramine and its main metabolite, norfenfluramine, have been examined pharmacokinetically using an analogue computer. A three compartment open model was proposed to simulate the biological processes with one peripheral compartment rapidly equilibrating with the central compartment and the second (tissue) compartment only slowly attaining equilibrium. Good agreement between experimental and computed data was obtained, although marked inter-subject variation was recorded. This was attributed to inter-subject differences in the three body compartments. Differences between the pharmacokinetic parameters obtained after oral and intravenous administration of fenfluramine indicated that the drug was significantly N-dealkylated in the intestine or on a first-pass through the liver.

The kinetics of absorption, metabolism, and excretion of (+)-amphetamine and (+)-methylamphetamine, after oral administration of “free” dosage forms to man, under controlled acidic urine conditions, have been examined using an electronic analogue computer. This device has also been used to determine the in vivo rate of release of the drugs from hard gelatin capsule dosage forms and prolonged-release preparations. In vivo drug release from the prolonged-release preparations was correlated with in vitro drug release data.

A mathematical model is described for an ideal sustained release dosage form in which there is a constant rate of release of drug from the maintenance dose. Kinetic equations related to this model are derived. The implications of these equations in the calculation of the dosage regimen for a sustained release product are considered.

The urinary excretion of N-(2-benzoyloxyethyl)norfenfluramine (JP 992) was examined in man with normal and acidic urine after oral administration of the drug; 86–100% of the dose was excreted in 48 h as metabolites of the drug having m-trifluoromethylbenzyl and benzoyl moieties, but no unchanged drug was detected. Norfenfluramine, N-2-hydroxyethylnorfenfluramine, and a metabolite, which on treatment with zinc and hydrochloric acid gave norfenfluramine, were excreted in urine. N-2-Hydroxyethylnorfenfluramine and a second unidentified metabolite were also excreted as both sulphate and glucuronide conjugates.

The paper chromatographic behaviour of a variety of amines both alone and in the presence of acids in acidic, neutral and basic running solvents is reported. Using a n-butanol: acetic acid: water solvent, multiple spot formation by several pure sympathomimetic amines was observed in the presence of the stronger organic acids. Many weaker acids affected the amines in a neutral solvent. The results emphasise the need for correct controls and the cautious interpretation of chromatograms of biological extracts since the number of spots produced is not necessarily indicative of the number of bases present.

The interaction of solutions containing oxine or iron or both (in a 1:1 molar ratio) with Staph, aureus is examined with respect to the chelating agent and metal ion binding by the bacteria. Iron enhances the amount of oxine uptake by the organism although the presence of the chelating agent does not affect the amount of iron bound. Iron is shown to be present in the ferric state in dilute solutions containing oxine. Two types of iron receptor sites in the bacterial surface are postulated and iron is shown to mediate oxine binding by the bacteria.

The urinary excretion of lignocaine and monoethylglycinexylidide (megx) has been studied in man. The finding that megx is a major metabolite of lignocaine in man is discussed in relation to studies in animals reported by other workers. An analogue computer model was constructed to simulate the metabolism and excretion of lignocaine. By varying the model parameters it was possible to obtain good agreement between the calculated and empirical excretion data for both lignocaine and its metabolite megx. Because of this good agreement, the computer was used to predict body levels of the compounds after a dose of lignocaine.

The muscarinic activities and rates of hydrolysis by acetylcholinesterase of the optical isomers of the acetyl-α- and acetyl-β-methylcholines of known configuration have been determined. The results have been correlated and the possible characteristics of muscarinic receptors outlined.

Nicotine and a basic metabolite, cotinine, were determined in the urine by gas-liquid chromatography after intravenous administration of (—)-nicotine hydrogen (+)-tartrate to groups of male and female smokers and non-smokers in whom the urine was maintained at an acid pH. The urinary recoveries of nicotine and cotinine from male smokers fell in two groups. One showed a lower recovery of both alkaloids than was seen with male non-smokers. The other showed a similar recovery of nicotine but more cotinine than the male non-smokers. Female smokers excreted less nicotine but more cotinine than female non-smokers. More nicotine but less cotinine was excreted by female non-smokers than by male non-smokers. The results show sex dependent metabolism of nicotine occurs in non-smoking humans and that smoking causes alterations in nicotine metabolism.

Summary The evidence is presented for the probability of the activity exhibited by analgesics and their antagonists being due to their association with a specific receptor surface. The configurations of those isomers exhibiting nearly all the activity of certain racemic mixtures are identical, and related to that of D-(–)-alanine; the stereochemical requirements of analgesics are considered. Active analgesics are shown to have structures which enable them to present similar surfaces to allow of their association with a proposed “analgesic receptor surface,” the essential features of which are described. A number of essential structures are outlined as prerequisites for compounds designed as analgesics.

Gas-liquid chromatography is a sensitive technique for the analysis of pentazocine in biological samples. Dose for dose, the concentration in blood and the urinary excretion rate of pentazocine are much lower after oral administration than after intravenous administration. The recovery of the unchanged drug in faeces is low whether it is given by mouth or intravenously.

The fragmentation of some alkyl-substituted-6,7-benzomorphans upon electron impact (70eV) is characteristic. The relative intensities of some ions varies in a predictable manner depending on the configuration of the C-9 hydrogen atom. Configuration and structure of 5,9-disubstituted-6,7-benzomorphans can be assigned by mass spectrometry even when only one isomer of a structure capable of existing in diastereoisomeric forms is available.

In the buccal test there is a linear relation between percentage absorption and alkyl chain length for a series of p-n-alkyl phenylacetic acids. Branching and cyclizing the alkyl chain reduces the percentage absorption. With the p-halogeno-acids, absorption increases as the atomic weight of the halogen atom increases; a chlorine atom is approximately equivalent to a methyl group in its effect on absorption. An oxygen atom between an alkyl group and ring is equivalent to reducing the chain length by one methylene group. The absorptions of α-methyl-substituted acids are greater than those of the unsubstituted acids.

The urinary excretion of ethylamphetamine and its metabolite amphetamine was studied in man after oral administration of (±)-, (+)-, and (-)-ethylamphetamine hydrochloride. The rates of excretion of these amines are dependant on the pH of the urine. At acid values, the (+)-isomer is metabolized faster and to a greater extent than the (-)-isomer, which is excreted mostly unchanged. The effect of alkyl chain length on stereoselective metabolism of N-alkylamphetamines is discussed.

The buccal absorption of amphetamine, methylamphetamine and dimethylamphetamine in solutions at pH 8·16 and 9·18, was measured in man after 1, 2, 3, 4, 5 and 10 min. The recovery of the drugs from the buccal membrane after uptake was also measured by washing out the mouth for varying times with buffer solutions. An analogue computer model of the biological system was used and the kinetic parameters for the buccal absorption of the amphetamines were calculated.

The treatment of quinine-selective adsorbents by steam, heat, in presence of water and by treatment with acid and dry organic solvents destroyed their selectivity whereas the adsorptive power of control adsorbents was almost unaffected by these treatments. A progressive increase in pH of the adsorbate solutions from pH 1 to 3 increased the adsorptive power of the selective adsorbents more than that of the control adsorbents. Increasing concentrations of sodium chloride in the adsorbate solutions increased the quinine-uptake on the adsorbents. Stereoselectivity is probably due to the formation of “footprints” in the surface of selective adsorbents. The similarities between the behaviour of active sites in biological surfaces and those in these stereoselective adsorbents are described.

Evaluation of the antibacterial activity of solutions containing hexylresorcinol in the presence and absence of cetomacrogol and sodium chloride is described. The relation between the extent of drug binding, light-scattering changes and the release of cell exudate in E. coli suspensions on addition of hexylresorcinol with the bactericidal activity is examined. Potentiation of the bactericidal activity of hexylresorcinol by sodium chloride and the inactivation by cetomacrogol is discussed with respect to drug binding, light-scattering changes in the bacterial suspensions and the release of bacterial cell exudate in the presence of these agents.

In alkaloids of the corynantheidine group, the rate of quaternization at N-4 and the pKa values give a measure of the degree of steric hindrance at this site due to the axial hydrogen at C-3 and the ethyl group at C-20. These hinder the availability of the lone pair of electrons on N-4 to electrophiles. Partition coefficients indicate that lipid solubility is associated with planarity of the molecules; this explains why the more planar isomers (allo and normal) are more highly metabolized in microsomes than the less planar isomers (pseudo and epiallo).

ALTHOUGH urinary excretion studies (Campbell, Nelson & Chapman, 1959; Chapman, Shenoy & Campbell, 1959; Shenoy, Chapman & Campbell, 1959) have been used as a technique to evaluate prolonged-release dosage forms of amphetamine, the significance of the results is in doubt because of the use of non-specific assay methods and the failure to control urinary pH. The use of radioactive material has indicated the similarity between a dose of 5 mg amphetamine three times a day and a 15 mg prolonged release preparation (Rosen, Tannenbaum, Ellison, Free & Crosley, 1965).

The urinary excretion of methylamphetamine and its metabolite, amphetamine, was studied after oral administration of (+)- and (–)-methylamphetamine hydrochloride to three male subjects. Fluctuations in the excretion rate of both amines occurred and were associated with changes in urinary pH. The fluctuations were abolished when the urine was maintained either acid or alkaline, by administration of ammonium chloride and sodium bicarbonate respectively. The total amount of both amines excreted was lower under alkaline than acid urine conditions. N-Demethylation of methylamphetamine was small, but greater for the (+)- than the (–)-isomer.

Isomeric methoxyoxindoles are metabolised by rats, guinea-pigs and rabbits to phenolic metabolites by O-demethylation and hydroxylation. This has been shown by comparison of the physical characteristics of the metabolites with those of standard synthetic hydroxyoxindoles. Negligible O-demethylation of methoxyoxindoles occurs with rat or guinea-pig liver microsome preparations, when compared with those of rabbit, but significant O-demethylation occurs with rat liver slices.

The gas-liquid chromatographic retention times of heteroyohimbine alkaloids on a 1% SE-30 column are in the order pseudo < epiallo < allo < normal. The introduction of one methoxy group into the indole nucleus doubles the retention time while two methoxy groups increase it by a factor of four. Binding of the indole nucleus reinforced by the suitably orientated lone pair electrons of the basic nitrogen to the liquid phase of the column in the important conformers of the various configurations, is used to explain the results.

Seven alkaloids, rotundifoline, isorotundifoline, rhynchophylline, isorhynchophylline, ciliaphylline, rhynchociline and mitraciliatine have been isolated from the leaves of Mitragyna ciliata Aubr. et Pellegr. The latter three are hitherto undescribed alkaloids.

After oral administration, diethylpropion is rapidly and extensively metabolized in man by N-de-ethylation and stereoselective carbonyl reduction. The unchanged drug excreted in acidic urine represents about 2% of the dose, while the total metabolites determined account for some 85%. The excretion curves indicate that the probable contribution of the parent compound to the observed activity is small. The major metabolites, together representing about 70% of the dose, are N-ethylaminopropiophenone, (+)-N-diethylnorpseudoephedrine, (+)-N-ethylnorpseudoephedrine, (-)-norephedrine and (-)-norpseudoephedrine. The other stereoisomers of the three amino-alcohols, and aminopropiophenone, are present in minor amounts.