Tiapamil, Ro 11-1781, a Ca++ antagonist. An improved synthesis, physiochemical properties, preparation of a deuterated derivative

An improved synthesis of tiapamil 3, Ro 11-1781, N-(3,4-dimethoxyphenethyl)-2-(3,4-dimethoxyphenyl)-N-methyl-m-dithiane-2- propylamine 1,1,3,3-tetraoxide is described. The structure of the corresponding hydrochloride monohydrate 4, a Ca++ antagonist has been confirmed by an X-ray crystallographic analysis. Since biotransformation of tiapamil into metabolites 5, 6 and 7 occurs mainly in the close vicinity of the nitrogen atom, compound 8 bearing seven deuterium atoms has been synthesised.

[Sigma-ligands for new therapeutic drugs]

Compounds that show their pharmacological actions via specific receptors are considered potential candidates for new drugs. Recently, several compounds that have specific binding sites and show certain pharmacological actions have been identified, but neither their binding sites, their endogenous substances, nor the functional role of the binding sites have been clarified. Regardless of the exact role of the binding sites of the compounds, research into the sites has opened up new areas of receptor investigation, and also new strategies for developing drugs. The sigma-ligand is one such kind of compound, and the existence of a binding site for the ligand was first postulated to account for the psychotomimetic effects of N-allylnormetazocine and related racemic benzomorphans. The binding site of the sigma-ligand is widely distributed in the central nervous system and peripheral systems. However, it still remain to be established whether sigma-ligand binding sites are to be referred to as "receptors". The classification of the ligands as agonists or antagonists at the sites and the heterogeneity and the functional role of the binding sites have not yet been clarified. Furthermore, the therapeutic targets have not been clearly determined. However, the sigma-ligands have high potential for developing new drugs. One of the possible targets of the sigma-ligands as new forms of drugs is schizophrenia. Recently, we identified two potent and highly selective sigma-ligands, FH-510 and NE-100. Together with the data on the binding properties and pharmacological actions of these compounds, the possibilities of the sigma-ligand as a new therapeutic drug were discussed.

Biodegradation and toxicity to fish of di-long-chain tertiary amine salt containing ester and amide bonds

Biodegradability of N-(3-alkanoylaminopropyl)-N-(2-alkanoyloxyethyl)-N- methylammonium chloride (EAA) was investigated. Biodegradabilities by biochemical oxygen demand (BOD) and dissolved organic carbon (DOC) after 28 days were 79 and 91%, respectively, and almost the same amount of ammonium ion as the theoretical value was detected using a modified MITI test (I) (OECD guidelines, 301C). In the test with activated sludge obtained from a municipal sewage treatment plant, biodegradabilities by BOD and DOC after 35 days were 87 and 98%, respectively, and the 1H-NMR analysis of the tested solution which was done separately under similar conditions indicated the rise and fall of two biodegradation intermediates. Therefore, EEA was considered to be a readily and ultimately biodegradable compound. Besides, the 96-hr LC50 value in red killifish (Oryzias latipes) of EAA was 66 mg/liter. More than 1000 mg/liter was of biodegradation intermediates rapidly made by biodegradation of EAA. These results reveal that EAA has sufficient environmental compatibility.

Pharmacokinetics of intravenous mexiletine in patients with acute myocardial infarction

Acute myocardial infarction (AMI) is known to alter the pharmacokinetics of several antiarrhythmic agents. To study the effects of AMI on the kinetics of mexiletine (MEX), a single intravenous dose of 200 mg MEX HCl was infused over 30 min in 11 patients with AMI. The study was performed within 24 h of the onset of pain (study I) and repeated about 2 weeks later in seven patients at discharge (study II). MEX was quantitated in plasma and urine samples by a gas-liquid chromatographic method. The decline of MEX in plasma was three-exponential, with a terminal half-life of 14.7 +/- 3.4 (mean +/- SE) h in study I and 11.3 +/- 2.4 h (p less than 0.05) in study II, in the seven patients studied in both phases. The steady-state volume of distribution averaged 578 +/- 97 L in study I and 415 +/- 33 L in study II (p less than 0.05). The total plasma clearance, renal clearance, and recovery of MEX in urine were similar in the two studies, as was the plasma protein binding of MEX (64 +/- 2 vs. 57 +/- 3%, NS). Thus, an increase in the volume of distribution with consequent prolongation of the elimination half-life of MEX occurs in the acute phase of AMI, whereas the rate of elimination remains unchanged.

[Demethylation of N-methylphenylalkylamines and propylhexedrin as well as of their N-formyl- and formyl)N-methoxymethyl analogues by rat liver homogenates (author's transl)]

The N-demethylation of various secondary N-methylphenylalkylamines and propylhexedrin in the 9.000-g-supernatant of rat liver homogenates is inhibited by introduction of a N-formyl group. Higher reaction rates for the O-methyl derivatives of pholedrin are attributable to an additional O-demethylation which is obviously favoured, when the N-demethylation is inhibited by the formyl group. The velocity of the oxidative degradation of the methoxymethyl group in formyl(N-methoxymethyl) analogues is markedly higher than the N-demethylation rates of the formyl)N-methyl) derivatives and depends to a greater extent upon the structure of the side-chain and the degree of hydrogenation of the nucleus.

Excretion and metabolism of the antihypertensive agent, RWJ-26240 (McN-5691) in dogs

The excretion and metabolism of a 2-ethynylbenzenealkanamine analog, antihypertensive RWJ-26240 (McN-5691), in beagle dogs was investigated. Recoveries of total radioactivity in urine and feces in the 7 days after oral administration of 14C-RWJ-26240 (6 mg/kg dose) were 2.8% and 96.8% of the radioactive dose, respectively. Representative plasma, urine, and fecal samples were pooled and purified for metabolite profiling, isolation, and identification. Unchanged RWJ-26240 (<19% of the dose) plus 12 metabolites were isolated and identified from these samples using chromatography (TLC, HPLC), spectroscopy (NMR, MS), and derivatization techniques. Unchanged RWJ-26240 plus identified metabolites accounted for >75% of the sample radioactivity in plasma and feces. The formation of RWJ-26240 metabolites can be depicted by the following proposed pathways: 1) N-demethylation, 2) O-demethylation, 3) phenyl hydroxylation, and 4) N-dealkylation. The first three pathways appeared to be quantitatively important steps which led to the production of four major metabolites (each >5% of the sample radioactivity). RWJ-26240 was extensively metabolized in the dog, and fecal excretion was the major route of elimination of RWJ-26240 and its metabolites.

Nicotinic-like effects and tissue disposition of isopropylamine

Previous studies in our laboratory have demonstrated that the acute sympathomimetic effects of isopropylamine are due to stimulation of autonomic ganglia. The present studies were designed to determine whether isopropylamine produced ganglionic blockade after its initial stimulation of autonomic ganglia. Infusion of isopropylamine (2.5 mg/kg/min) produced an initial increase in arterial pressure and heart rate which was followed by a prolonged hypotension and bradycardia; lower doses produced only a hypotensive response. After infusion of isopropylamine, the positive chronotropic responses to preganglionic cardioaccelerator nerve stimulation were significantly reduced, whereas the responses to postganglionic nerve stimulation were essentially unchanged. Similarly, the negative chronotropic responses to peripheral vagal stimulation were significantly reduced after isopropylamine administration. Moreover, isopropylamine reduced the cardiovascular responses to i.v. injections of the ganglion nicotinic stimulant, dimethylphenylpiperazinium iodide. Studies on the disposition of isopropylamine indicated that there was significant cumulation of isopropylamine in all tissues as compared to plasma. When the relationship between plasma isopropylamine and the decreases in mean arterial pressure was examined, a significant positive correlation (r = 0.87) was found. These results indicate that isopropylamine has both ganglion stimulating and blocking properties and is similar in its action to the classical nicotinic ganglion stimulant drugs such as dimethylphenylpiperazinium iodide and tetramethylammonium.

The selective norepinephrine reuptake inhibitor, LY368975, reduces food consumption in animal models of feeding

The compound, LY368975 ((R)-thionisoxetine) is a potent and selective inhibitor of the norepinephrine (NE) reuptake site. We evaluated the in vivo properties of LY368975 in various animal models. In mice, LY368975 prevented heart NE depletion by 6-hydroxydopamine with an ED50 of 1.22 mg/kg. In rats, orally administered LY368975 inhibited 3H-NE uptake into hypothalamic synaptosomes ex vivo with an ED50 of 2.5 mg/kg and 3H-tomoxetine binding to the NE transporter with an ED50 of 2.7 mg/kg. When rats were deprived of food for 18 hr, 10 mg/kg LY368975 was able to suppress food intake 1, 2 and 4 hr after reintroduction of the feed. In nonfasted rats trained to drink sweetened condensed milk, LY368975 produced a dose-dependent reduction in consumption with a 44% decrease at 3 mg/kg. At doses up to 10 mg/kg p.o., LY368975 produced no significant effects on locomotor activity suggesting the compound does not activate or sedate the animals at pharmacologically relevant doses. Therefore, LY368975 is an orally available and centrally active NE reuptake inhibitor that is capable of reducing food consumption in rodents. Compounds of this class may have use in the treatment of obesity and eating disorders.

[Pharmacological analysis of drug interactions of disopyramide and its congeners with peripheral muscarinic acetylcholine receptors]

The interactions of the antiarrhythmic agents, disopyramide (D) and its congeners, pirmenol (Pr) and pentisomide (Pt), with peripheral muscarinic receptors (m-AchR) were investigated using binding and functional assays. D, Pr and Pt inhibited the specific binding of [3H]-N-methyl scopolamine ([3H]-NMS) to membrane fractions prepared from guinea pig left atria (LA), submandibular glands (SG) and urinary bladders (UB) in a concentration-dependent manner. Computer-assisted analysis showed that the displacement curves with D obtained from LA and UB were shallow and best fitted by a two-site model, whereas D interacted with a single class of binding sites in SG. Kinetic experiments measuring [3H]-NMS dissociation revealed the existence of allosteric interaction of D with m-AChR, and it might be responsible for the low affinity components of the displacement curves in LA and UB. The pKi values for D in high-affinity receptor sites in LA and UB (pKH) were very close to the pKi for D obtained in SG, and corresponded well to the pA2 values of around 6.0 for antagonism against the carbachol-induced mechanical responses of LA and UB. Pt interacted with m-AChR with qualitatively very similar fashion to that of D, but its potency was very weak (1/10 of D). Pr interacted with a single class of binding sites in LA and SG with pKi of 6.02 and 5.18, respectively, indicating that the affinity of Pr to glandular m-AChR (M3) was 7 fold lower than that to cardiac one (M2). The displacement curve with Pr in UB was best fitted by a two-site model with pKH of 5.93 and pKL of 5.20. The pA2 for Pr in LA and UB were 6.47 and 5.55, respectively, suggesting the existence of a mixed population of M2 and M3 in UB and the contribution of M3 to its contractile response. It is concluded that Pr is able to distinguish M2 from M3, and that D and Pt have almost similar affinity to both subtypes of m-AChR. Pr was less potent than D in interaction with M3.

Steady-state kinetic analysis for the reaction of ammonium and alkylammonium ions with methylamine dehydrogenase from bacterium W3A1

The steady-state kinetic mechanism for the reaction of n-alkylamines and phenazine ethosulfate (PES) or phenazine methosulfate (PMS) with methylamine dehydrogenase from bacterium W3A1 is found to be of the ping-pong type. This conclusion is based on the observations that 1/v versus 1/[methylamine] or 1/[butylamine] plots, at various constant concentrations of an oxidizing substrate, and 1/v versus 1/[PES] or 1/[PMS] plots, at various constant concentrations of a reducing substrate, are parallel. Additionally, the values of kcat/Km for four n-alkylamines are identical when PES is the oxidizing substrate, as were the kcat/Km values for four reoxidizing substrates when methylamine was the reducing substrate. Last, analysis of steady-state kinetic data obtained when methylamine and propylamine are presented to the enzyme simultaneously and PES and PMS are used simultaneously also supports the involvement of a ping-pong mechanism. The enzymic reaction with either methylamine or PES is dependent on the ionic strength, and the data indicate that each interacts with an anionic site on methylamine dehydrogenase. The presence of ammonium ion at low concentration activates the enzyme, but at high concentration this ion is a competitive inhibitor in the reaction involving methylamine and the enzyme. A complete steady-state mechanism describing these ammonia effects is presented and is discussed in light of the nature of the pyrroloquinoline quinone cofactor covalently bound to the enzyme.

Distribution of citalopram in the blood serum and in the central nervous system of rats after single and multiple dosage

Distribution in rat tissues of citalopram, a potent and specific inhibitor of neuronal 5-HT uptake was uneven. The blood serum level of the drug did not reflect its distribution in the brain tissue and in the spinal cord. Prolonged administration of citalopram enhanced its blood serum, brain and spinal cord AUC values and slowed down its elimination from all investigated tissues. In contrast to imipramine, citalopram penetrated easily to the spinal cord.

The pharmacology of 1-phenyl-2-propylamino-pentane (PPAP), a deprenyl-derived new spectrum psychostimulant

The peculiar tyramine uptake inhibitory effect of (-)deprenyl prompted structure-activity relationship studies aiming to develop new spectrum central nervous system stimulants which are devoid of MAO inhibitory potency and operate de facto as indirectly acting, nonreleasing sympathomimetics. Of the derivatives synthesized for this purpose, 1-phenyl-2-propylaminopentane (PPAP) was selected as the reference substance and its pharmacological spectrum is presented. PPAP is taken up by the catecholamine axon terminal membrane and the vesicular membrane but it is devoid of catecholamine-releasing property. As a result, PPAP is, by interference, a potent inhibitor of the uptake of indirectly acting sympathomimetic releasers and of the catecholamine transmitters. This was proved, on the one hand, by measuring the uptake of [14C]PPAP into the catecholaminergic axon terminals and the inhibition of the uptake of [3H]noradrenaline and [3H]dopamine by PPAP in the rat brain, and, on the other hand, on the pulmonary artery strip of the rabbit and, in vivo, using the rat nictitating membrane as a detector. PPAP increases motility at 2 mg/kg and, in contrast to amphetamine, inhibits it at very high doses (50 mg/kg) only. A two-sided antagonism in the motility-increasing effect between PPAP and amphetamine and, more pronounced, between PPAP and mazindol was detected. PPAP is substantially less effective in inducing stereotyped behavior than either amphetamine or methamphetamine. PPAP facilitates learning and retention, is highly potent in antagonizing the tetrabenazine-induced depression in behavioral tests and is very effective in the forced swimming test. Whereas amphetamines facilitate performance in a very narrow range of low doses, which turns, at a modest elevation of the dose, into the opposite effect, PPAP improves performance within a reasonably broad dose range. Based on the peculiar pharmacological profile of PPAP, its potential usefulness in depression, in Alzheimer's disease and in attention-deficit-hyperkinetic disorder seems to be plausible.

Turnover of putrescine in a Pseudomonas species

A Pseudomonas species was found to readily take up labeled putrescine added in trace amounts to any of four growth media, bis-(3-aminopropyl)-amine, 4-aminobutyrate, glucose-NH(3), and Casamino Acids, although the rate of uptake varied considerably from one medium to another. Putrescine degradation, as well as excretion and conversion to hydroxyputrescine, was demonstrated in all four media, indicating that this organism has a constitutive putrescine degradation pathway. The extents of putrescine degradation, excretion, and conversion to hydroxyputrescine are shown for these four growth media through an incubation period of 1 hr. These results document more fully the experimental details behind a previous communication which postulated that the constitutive degradation of putrescine participates in the regulation of intracellular putrescine concentration. The significance of this apparent violation of the general concept that synthetic end products are normally not degraded is discussed.