Plasma concentrations and bioavailability of clofibric acid from its calcium salt in humans

The bioavailability of clofibric acid from formulations containing calcium clofibrate along and mixed with calcium carbonate (1:1 w/w) was compared to that from a standard clofibrate formulation in a crossover study in 12 human subjects. The 95% confidence intervals of bioavailability differences were such that they were unlikely to be detected in clinical practice; all three formulations may be considered bioequivalent, although the bioavailability rate was probably greater from the formulation containing calcium clofibrate alone. Peaks of mean concentrations of 80 +/- 13,67 +/- 16, and 64 +/- 18 microgram/ml +/- SD occurred after administration of 853 mg of clofibric acid calcium salt alone, 809 mg of clofibric acid calcium salt mixed with calcium carbonate, and 885 mg of clofibrate, respectively; mean concentrations declined from peak levels with half-lives of 15-17 hr.

Disposition of the hypoglycaemic sulphonylurea CS 476

The disposition of radioactivity was studied after administration of a new oral hypoglycaemic agent, 14C-labelled CS 476, to rats, rabbits and dogs at a pharmacologically active dose level of 0.2 mg/kg and to human subjects at a therapeutic dose level of 5 mg. After oral doses, most of the drug was excreted in the faeces by rats and dogs and faecal radioactivity was obtained from biliary excretion. Rabbits and humans excreted most of the dose in urine. Unchanged CS 476 was the major radioactive component in the plasma of all the species during 6 hours after dosing, and was extensively bound to the plasma proteins. The half-life of CS 476 in plasma was 2 hours in dogs and humans, and 16 hours in rabbits. Drug accumulation did not occur in dog and rabbit plasma during a period of consecutive daily doses and the half-lives after the last of the repeated doses were similar to those found after single doses. In rats, plasma concentrations were relatively low, and did not reach the peak level found in female rats until 24 hours after dosing. CS 476 was extensively biotransformed. The apparent species-dependent disposition of CS 476 may explain differences in tolerance to chronic doses.

Plasma isosorbide dinitrate concentrations in human subjects after administration of standard and sustained-release formulations

After sublingual administration of 5 mg of isosorbide dinitrate, mean plasma concentrations (+/-SD) peaked (8.9+/-3.1 ng/ml) at 15 min after dosing and declined with a half-life of 30 min. After oral administration of 5 mg, mean concentrations peaked (3.1+/-0.7 ng/ml) at 30 min and declined with a half-life of 40 min. After oral administration of 20 mg in a sustained-release tablet, mean concentrations initially peaked (1.4+/-1.2 ng/ml) at 40 min, declining to 0.9+/-0.5 ng/ml after 8 hr. Mean concentrations were maintained above half the mean peak level during 10 hr. Because of probable rapid first-pass metabolism, the bioavailability of isosorbide dinitrate after administration of the oral dose of the standard tablet was 58% of that from the sublingual dose, and the bioavailability from the sustained-release tablet was 47% of that from the sublingual dose of the standard tablet. The time course of mean plasma concentration data could be described by a one-compartment model; but a more complex model, taking the pass effect into account, probably is needed for a better description of the pharmacokinetics of isosorbide dinitrate.

Plasma concentrations, bioavailability and dissolution of chlorpropamide

The bioavailability of chlorpropamide from two new formulations (Melitase tablets) has been compared to that from a reference formulation which is currently in clinical use as a hypoglycaemic agent. In both rate and extent of bioavailability, all three formulations may be considered equivalent, providing allowances are made for differences in drug content. With 95% confidence, the mean bioavailability of chlorpropamide from the new formulations was within about 16% of the mean from the reference formulaion, and formulation-related differences were not statistically significant. Although all three formulations were shown to have similar dissolution profiles, dissolution of chlorpropamide was pH-dependent in vitro. Dissolution was almost complete during 30 min at pH 7.2, but only 40%-60% had dissolved during 90 min at pH 2.0. A peak mean concentration of 22.7 mug/ml was reached 3 h after administration of 2 x 100 mg tablets of the new formulation and peak mean concentrations of 26.8 mug/ml and 27.4 mug/ml were reached 3 h and 4 hours after administration of one 250 mg tablet of the new formulation and one 250 mg tablet of the reference formulation respectively. Formulation-related differences of mean plasma concentrations (after scaling for equal doses of 250mg) were not significant and each formulation provided similar plasma concentrations at corresponding times after administration. Statistically significant subject-related differences in all the parameters of bioavailability were shown by analyses of variance.

The relation of deviant symptoms and behaviour in a normal population to subsequent delinquency and maladjustment

A survey of more than 6000 school children in 1961 established norms for symptomatology and behavior at ages 5-15. A follow-up to 1968 identified all children from the survey attending a child guidance clinic or appearing in court within that time. Those thus identified contained a significantly high proportion of boys who were reported as having more than 3 deviant items (i.e. occurring in approximately 10% of subjects in 1961). Specific health and behavioural items were found to have been reported in 1961 in proportions which were significantly different for children later appearing in child guidance clinic from those appearing in court. The amount of concern expressed by their parents over psychological and behavioural items distinguished court from clinic boys, while the concern shown by parents over items of physical health showed little difference in these 2 groups.

Serum concentrations and bioavailability of rifampicin and isoniazid in combination

The bioavailability of rifampicin and isoniazid from formulations containing these drugs in combination has been compared to that from formulations containing either drug alone. No formulation-related differences in either rates or extent of bioavailability were found after administration of each formulation. Mean peak serum concentrations of rifampicin (8.2-11.7 mug/ml) occurring 2 to 4 h after doses of 600 mg, and isoniazid (3.6-4.8 mug/ml) occurring 0.5 to 1 h after doses of 300 mg, were similar to those reported in the literature.

Serum concentrations of methaqualone after repeated oral doses of a combination formulation to human subjects

Concentrations of methaqualone have been measured in the serum of five male human subjects receiving five consecutive evening doses of a combination formulation containing methaqualone (250 mg), carbromal (300 mg) and benactyzine (0.33 mg) in each tablet. After administration of the first dose, mean peak serum concentrations of methaqualone (1.2 mug/ml) occurred at 3 h. After obtaining peak levels, mean concentrations of methaqualone declined rapidly during the next 6 h and thereafter more slowly during the next 18 h. After administration of the last (fifth) dose, mean peak serum concentrations of methaqualone (1.9 mug/ml; 1.5 mug/ml above the predose level) occurred at 2 h. After attaining peak levels, mean concentrations of methaqualone declined rapidly during the next 6 h, and thereafter more slowly, with a half-life of approximately 10 h. Mean concentrations of methaqualone in serum samples 24 h after the second, third, fourth or fifth doses were not significantly different (0.3 mug/ml - 0.6 mug/ml) during this period of dosing. This suggests that significant accumulation of methaqualone in the serum did not occur during a period of five consecutive evening doses of the combination formulation.

The metabolic fate of the coronary vasodilator 4-(3,4,5-Trimethoxycinnamoyl)-1-(N-pyrrolidinocarbonylmethyl)piperazine (cinepazide) in the rat, dog and man

1. An oral dose of the coronary vasodilator 4-(3,4,5-trimethoxy[14C]cinnamoyl)-1-(N-pyrrolidinocarbonylmethyl)piperazine was well absorbed and more than 60% of the dose was excreted within 24 h. In 5 days, rats, dogs, and man excreted in the urine and faeces respectively 36.7% and 58.3%, 33.4% and 68.6%, and 61.3% and 38.1% dose. Faecal radioactivity was probably excreted via the bile. 2. Plasma concentrations of radioactivity reached a maximum within about 1 h in all three species and declined fairly rapidly (t0.5 less than 3 h). For several hours, more than 50% of the plasma radioactivity was due to unchanged drug. After correction for dose and body weight (normalization), peak plasma concentrations of unchanged drug in man, rat and dog were in the approximate ratio 100 :30:1. 3. Similar metabolites were excreted by the three species, but the relative proportions differed. Rats and man excreted 17.2% and 15.9% respectively as unchanged drug in the urine whereas dogs excreted only 3.6%. Rat bile and urine contained 4.3% and 9.8% dose respectively as glucuronides of the mono-O-demethylated compounds and dog and human urine contained 9.0% and 2.6% respectively of these metabolites. The corresponding pyrrolidone accounted for 2.5%, 5.5% and 5.1% respectively in rat, dog and human urine. Complete O-demethylation also occurred since 4-(3,4,5-trihydroxycinnamoyl)-1-(N-pyrrolidinocarbonylmethyl)piperazine was present in rat faeces (22.1% dose).

Use of pharmacokinetics to predict the distribution of pantothenate in dogs

On the basis of plasma concentrations of pantothen[14C]ate, after its intravenous administration, a three compartment open model was proposed to predict the pharmacokinetics of pantothenate in dogs. The model assumed a central compartment comprising the plasma and other extracellular fluids, and distribution into two other peripheral compartments, one of which included the liver. Elimination of unchanged pantothenate was assumed to occur by metabolism from the compartment which included the liver. Distribution of pantothen[14C]ate from the plasma compartment into the liver compartment was shown to be very rapid; during 10 min after intravenous administration about 80 per cent of the dose had been cleared from the plasma compartment. The model successfully predicted the influence (first pass effect) of the liver on the fraction of an oral dose which reached the peripheral plasma unchanged.

Topical analgesia before tracheal intubation

The major toxic effects of local analgesic drugs are regarded as due to over-dosage. A technique of topical analgesia for tracheal intubation using lignocaine is described based on spraying the pyriform fossae to effect a superior laryngeal nerve block combined with topical analgesia of larynx and trachea which avoids excessive exposure of the lowere airway to the local analgesic. The results show lower levels of venous blood lignocaine with slower absorption of the agent than when similar doses are applied to the trachea. This method is accordingly recommended.

Oestrogen formation in human foetuses perfused with (4-14 C) progesterone

Four human foetuses of 16–20 weeks gestation were perfused via the umbilical vein with blood containing [4-14C]progesterone. Steroids were subsequently extracted from the livers, ovaries, adrenals and perfusates. Oestriol, containing a 14C-label was isolated and characterised from extracts of the livers, and in one case, the perfusate. Androstenedione, testosterone, oestrone and oestradiol were not present in any of the tissues in identifiable amounts.

The results demonstrate that the mid-term foetus, can form oestriol from progesterone independently of placental aromatisation.

Human foetal synthesis of testosterone from perfused progesterone

Two male and four female human foetuses of 16–20 weeks gestation were perfused with [4-14C]progesterone. Subsequently, testosterone and androstenedione bearing a 14C-label were isolated in significant amounts from the testes and adrenals, respectively, of the male foetuses. Both C19-steroids were also isolated from the perfusate of one of the male foetuses. Neither C19-steroid was present in the livers of the male foetuses or in the ovaries, adrenals, livers or perfusates of the female foetuses.

It is concluded that the mid-term male foetus can readily synthesize testosterone from the large amounts of progesterone of placental origin present in the foetal circulation. The results suggest that the conversion is primarily a testicular function, but a direct or indirect adrenal involvement cannot be excluded.

Human foetal adrenal 4-ene-3-oxosteroid synthesis: an investigation of (4- 14 C) pregnenolone and (4- 14 C)-dehydroepiandrosterone metabolism using new techniques

Human foetal adrenal slices were incubated with [4-14C]pregnenolone (20 foetuses) and [4-14C]dehydroepiandrosterone (18 foetuses). Product 4-ene-3-oxosteroids were isolated as a group and measured in toto by a double isotope dilution procedure. Production of compounds of the 4-ene-3-oxosteroid fraction was estimated over several time-intervals and relative to the protein content of the incubated tissue.

No conversion of [4-14C]pregnenolone by foetal adrenal tissue to 4-ene-3-oxosteroids was detectable although metabolism of the substrate to other compounds was indicated. Conversion of [4-14C]dehydroepiandrosterone to 4-ene-3-oxosteroids, principally androstenedione, occurred in incubations of tissue from 7 of the 10 male foetuses studied with this substrate, and from 2 of undetermined sex, but not from 6 female foetuses so studied. Testosterone formation from [4-14C]dehydroepiandrosterone was not detectable. There was no apparent variation in 4-ene-3-oxosteroid formation relative to foetal age in the range investigated (approximately 6–20 foetal weeks).

These results are interpreted, in the light of previous studies, as giving credence to the concept of substrate specificity in human foetal adrenal 4-ene-3-oxosteroid formation. The evidence that foetal adrenal androstenedione formation may be sex-dependent is considered, and the implications discussed.