High-pressure liquid chromatographic analysis of cimetidine, a histamine H2-receptor antagonist, in blood and urine

A method is described for extraction of cimetidine, a histamine H2-receptor antagonist, from whole blood and urine with subsequent analysis by high-pressure liquid chromatography (HPLC). The drug is extracted from biological fluids with 1-octanol and back-extracted into dilute acid and then into a small volume of ethanol by saturation with potassium carbonate. HPLC analysis is performed on a column of 5-micrometer silica with a mixed mobile phase consisting primarily of acetonitrile. The method measures concentrations of cimetidine as low as 0.05 microgram/ml and is reproducible. Blood levels and urinary excretion data obtained with the analytical procedure are given for a group of human subjects who received 200-mg oral doses of cimetidine.

The plasma protein binding and distribution of etomidate in dog, rat and human blood

The interactions of etomidate and its major metabolite (R 28 141) with plasma proteins were studied by equilibrium dialysis with a multiple cell system. A 4% human serum albumin solution was able to bind 78.5% of the etomidate, and 60.5% of R 25 141, whereas a 1.5% human gamma globulin solution bound etomidate for not more than 3% and did not bind R 28 141 at all. The association constants and free binding energies for the binding of etomidate and R 28 141 to human serum albumin were determined. Plasma protein binding of etomidate was 75.4% in the dog and 76.5% in man; in rat plasma 79.5% of the radioactivity was bound to the plasma proteins, however the etomidate was partly hydrolyzed, even in the presence of sodium fluoride. In the rat 29.7% was distributed to the blood cells, 55.9% bound to plasma proteins and 14.4% was present in plasma water; in the dog the distribution percentages were 42.1%, 43.7% and 14.2% respectively, and in man 37.7%, 47.6% and 14.7% respectively. The major metabolite of etomidate was distributed for 26.3% to the human blood cells, 47.4% was bound to plasma proteins and 26.2% was present in the plasma water; its plasma protein binding amounted to 64.3%. Etomidate was bound at or in the blood cells, whereas R 28 141 was not.

Cimetidine suppression of nocturnal gastric secretion in active duodenal ulcer

Nocturnal pain and gastric hypersecretion are common in duodenal ulcer. Therefore, we investigated the antisecretory effects of a new H2-receptor antagonist, cimetidine, in 200-, 300- or 400-mg doses, taken orally at bedtime. The 200-mg dose did not cause a statistically significant change in nocturnal (midnight to 7 a.m.) acid output and had only a borderline effect on pH. However, the 300-mg and 400-mg doses significantly (P less than 0.001) lowered acid output and increased (P less than 0.01) intragastric pH. All doses caused substantial decreases in secretory volume output. After a 400-mg dose, half the patients remained anacidic for eight hours. Dose-related increases of drug blood levels were observed and correlated with the degree and duration of inhibition of acid output. Serum gastrin levels were unaffected. Cimetidine appears to be a potent inhibitor of nocturnal gastric secretion.

Metabolism of histamine in secreting and isolated canine stomach

Total 14C activity in juice secreted by gastric pouches of six dogs and seven isolated canine stomachs was determined in response to intravenous and intra-arterial infusions of histamine and [14C]histamine. The proportions of 14C attributable to histamine, Nalpha-methylhistamine (NalphaMeH), Nalpha,Nalpha-dimethylhistamine (NalphaNalphaMe2H), N-telle-methylhistamine (NtauMeH), imidazole acetic acid (ImAA), N-methylimidazole acetic acid (NtauMeImAA), acetylhistamine (AcH), and histaminol (HOH) were defined using thin-layer chromatography. Similar estimates were made at the end of infusions on blood, gastric mucosa, and gastric muscle. Methylation was the major, or sole, route of metabolism of histamine in the gastric mucosa, and the major product was inactive NtauMeH. Small quantities of the active NalphaMe derivatives, particularly NalphaNalphaMe2H, were identified in both the juice and mucosa. Little or no ImAA, NtauMeImAA, AcH, and HOH were present in juice from isolated stomachs while they did occur in the juice from intact dogs, demonstrating they are extragastric metabolites of histamine. A major mucosal function of methylation of histamine is inactivation, although NalphaMe derivatives formed may play a role in the secretagogue action of histamine.

Influence of a meal on the absorption of cimetidine. A new histamine H2-receptor antagonist

Absorption of an oral dose of 300 mg of Cimetidine was studied after an overnight fast in six healthy male volunteers on three separate occasions, 20 min before, during, and 2 h after a standard breakfast. Compared to the doses taken before and after the meal, the dose taken with the meal showed a significant delay in the time taken to reach therapeutic blood concentrations of the drug with no reduction in the period of time during which this concentration was maintained. We, therefore, suggest that the drug should be taken with a meal to achieve optimal acid inhibition in the interdigestive period.

24-hour control of intragastric acidity by cimetidine in duodenal-ulcer patients

The effects of two dose regimens of cimetidine on 24 h intragastric acidity were investigated in six patients with duodenal ulcer. They received placebo capsules on the first day and cimetidine on the second day. Cimetidine 0-8 g/day decreased 24 h mean H+ activity by 55% but 1-6 g/day decreased it by 67%, the difference being due to a greater nocturnal decrease in the high-dose group. Intragastric pH remained below 2-0 for much of the treatment day but similar values were found in four post-vagotomy patients. Cimetidine 0-8-1-6 g/day results in a decrease of intragastric acidity that is compatible with successful medical treatment of duodenal ulceration.

Miconazole in coccidioidomycosis. I. Assays of activity in mice and in vitro

Administration of miconazole to mice infected with Coccidioides immitis prevented death in all cases; the infecting doses killed 60%-100% of the untreated animals. The drug's anticoccidioidal influence was also demonstrated by its capacity to limit fungal proliferation in the lungs. The endospore phase of C. immitis, which predominates in lesions, was more susceptible to miconazole than were the saprophytic arthrospore and mycelial phases. The drug was lethal to endospores in vitro in the presence or absence of human plasma, but plasma decelerated the rate of killing. A sensitive quantitative assay (using endospores) for the drug in plasma was developed, and the inefficacy of determining the sensitivity of strains with mycelia was demonstrated.

Distribution, metabolism and excretion of etomidate, a short-acting hypnotic drug, in the rat. Comparative study of (R)-(+)-(--)-Etomidate

Tritium-labelled (R)-(+) and (S)-(--)-etomidate was injected intravenously in male Wistar rats at four dose levels. Initial plasma clearance was high and the largest part of etomidate was rapidly distributed over those tissues, that had entered in equilibrium with plasma, such as brain, erythrocytes, heart, spleen, lung, kidney, muscle and intestines. Only in subcutaneous fat, testicles and stomach peak levels appeared after 28 minutes. The levels of etomidate, observed in all these tissues varied proportionally with the dose. Although the contents in brain of thw two isomers were comparable, only (R)-(+)-etomidate possesses hypnotic activity. The concentration in brain of (R)-(+)-etomidate, producing hypnotic activity in rats, was 1.50 +/- 0.35 mug/g tissues. Peak levels in liver appeared shortly after administration. Capacity-limited ester hydrolysis in the liver was the main metabolic pathway, yielding a single amphoteric metabolite. The rate of metabolization of (R)-(+)-etomidate was higher than that of the (S)-(--)-isomer. Excretion of the metabolite was mainly with the urine.

[Serum level and urinary excretion of 14C-thiamozol in patients with hyperthyroidism (author's transl)]

2-(14C) Thiamazol (Favistan) was administered intravenously in a therapeutically subthreshold dose to seven control subjects and five patients with hyperthyroidism. In both groups the reduction of plasma radioactivity occurred with at least two exponentials. Half-life was calculated to be 35 minutes for the faster and 28 hours for the slower process in the control group, and 12 minutes and about 20 hours, respectively, in the hyperthyroid patients. Forty-eight hour urinary excretion of the injected radioactive material was about 80% for the hyperthyroid patients and 87% for the control subjects. Maximal activity in urine occurred about six hours after injection. There was practically no demonstrable plasma-protein binding of the drug in in-vitro experiments. As the pharmacokinetics of the drug are not influenced in thyroid disease, there is apparently no need to adapt thyrostatic dosage in hyperthyroid states.

Imidazole in organs of inbred chickens selected for resistance or susceptibility to lymphoid leukosis or Marek's disease

Total and soluble imidazole was determined on samples of liver and kidney and soluble imidazole was determined on blood from eight strains of chickens selected at three locations for resistance or susceptibility to lymphoid leukosis and/or Marek's disease. Liver and kidney total and soluble imidazole was not different between strains classed as resistant or susceptible to lymphoid leukosis and/or Marek's disease. The weighted average of soluble blood imidazole was higher (P smaller than 0.01) in strains classed as resistant to lymphoid leukosis. A similar difference (P smaller than 0.01) was observed with strains classed as resistant or susceptible to Marek's disease when the selections from one location were not included in the weighted average.

The objective and timing of drug disposition studies, appendix I. Species differences in the tissue distribution of metazimid, an imidazolone derivative

A marked species difference has been observed in the tissue distribution of metazimid in the rat vs the dog after repeated doses. Differences in toxicity between these species are consistent with tissue levels but not plasma levels. No species differences in patterns of drug metabolism could be found in association with the marked difference in tissue cumulation.

Effect of histamine H2-receptor blockade on vagally induced gastric secretion in man

Metiamide, an antagonist of histamine H(2) receptors, was administered intravenously to normal subjects and to patients with a peptic ulcer during vagal stimulation with a constant infusion of insulin. In normal and peptic-ulcer subjects there were reductions of 70% and 71% respectively in gastric-acid output compared with control tests on the same subjects. The decreased acid output resulted from a reduction in both volume of secretion and acid concentration. Metiamide is therefore a potent inhibitor of vagally-induced gastric acid secretion.

Laboratory assessment of the antimycotic drug clotrimazole

Laboratory studies on clotrimazole showed that it had marked activity in vitro against all the Candida spp. and Cryptococcus spp. tested, against almost all strains of dermatophytes, and against Aspergillus spp and other fungal genera responsible for systemic mycoses; it had limited activity towards Gram-positive bacteria. The majority of Candida strains required MICs below 1 mug/ml and MCCs below 2 mug/ml.Serum, urine, and faecal assays of clotrimazole were made by microbiological methods on five children who received 100 mg/kg/day clotrimazole for several weeks. In-vitro sensitivity tests and biological fluid drug assays are also reported on specimens from 18 patients in other hospitals receiving clotrimazole for severe candidosis; several were renal transplant cases. Similar investigations are reported on specimens from 18 patients with pulmonary aspergilloses. The significance of low levels of the drug in body fluids, even after prolonged therapy, is discussed, and it is suggested that clotrimazole may be the first of a long series of imidazole derivatives with varying pharmacological and therapeutic properties.