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Biomedical subjects

R G Leonard

Publications and source records attributed to R G Leonard.

7 recordsLinked to original sources
PubMed1983

Vaginal absorption of hexachlorophene during labor.

Surgical soap that contains hexachlorophene is used as an antiseptic lubricant for vaginal examinations during labor in some centers. Theoretically, hexachlorophene can be absorbed from the vaginal mucosa and be potentially toxic to the fetus and neonate. To evaluate vaginal absorption and placental transfer of hexachlorophene, we measured levels in mixed arterial/venous cord serum and postpartum maternal serum in 28 women whose vaginal examinations were lubricated with pHisoHex during labor. The serum of 12 women had detectable levels of hexachlorophene, with a high level of 942 ng/ml. Cord serum had detectable levels in nine neonates, with a high level of 617 ng/ml. The conclusion is that hexachlorophene from vaginal lubricants is variably absorbed from the vaginal mucosa, and appreciable amounts can be detected in maternal and cord serum. Because of the potential for neonatal hexachlorophene toxicity, we recommend the use of alternative lubricants for pelvic examinations during labor.

Absorption↗
PubMed1979

Single-dose fasting bioequivalence assessment of erythromycin stearate tablets in man.

The bioequivalence of film-coated erythromycin stearate tablets produced by five different manufacturers was evaluated in a balanced incomplete block design involving the five formulations given to 30 fasted subjects over a 3-week study period. Serum levels of erythromycin activity were determined microbiologically. Statistical analysis of variance was performed on the observed bioavailability parameters: maximum serum concentration (Cmax), time to maximum serum concentration (Tmax), and area under the serum concentration-time curve (AUC). There was no statistical difference between formulations for the Tmax parameter. Formulation differences were found, however, based on the analysis of variance of the Cmax and AUC parameters. Two products, although not significantly different from one another, showed significantly greater Cmax and AUC values than the other three products.

Adult↗
PubMed1978

Bioavailability of acetazolamide tablets.

Plasma acetazolamide levels were measured by an enzymatic assay following single 250-mg oral tablet doses to 20 healthy volunteers; five different lots of acetazolamide tablets from a single manufacturer were used in a balanced incomplete block design. From the measured plasma levels, estimates of the bioavailability parameters (area under the plasma concentration versus time curve, time to peak plasma concentration, and peak plasm concentration) were obtained by least-squares digital computer fitting. No significant differences among the tablets were observed (alpha = 0.05) for the analysis of variance of the area under the curve or time to peak parameters. Two tablets, however, provided statistically higher peak plasma concentrations than the other three. Thus, lot-to-lot bioinequivalence of acetazolamide tablets was observed. Some in vitro tests employed showed general trends for correlation with the in vivo data. However, considerable refinement of these technique appears necessary for in vitro prediction of the observed lot-to-lot bioinequivalence.

Acetazolamide↗
PubMedDate not supplied

Calcium-channel blocking agents.

The role of calcium in the cardiovascular system, and the pharmacology, pharmacokinetics, and studies evaluating the clinical use of three calcium-channel blocking agents--verapamil hydrochloride, nifedipine, and diltiazem hydrochloride--are reviewed. Inhibition of calcium conductance and alteration of calcium availability cause profound changes in: slow inward current of the cardiac action potential, myocardial contractility and metabolism, blood pressure regulation, and smooth-muscle activity. Calcium-channel blocking agents affect the movement of calcium through these channels in smooth and cardiac muscle; the specific agents in this class differ markedly in their inhibitory effects. Verapamil hydrochloride is useful intravenously for treating supraventricular rhythm disturbances. It is absorbed well when taken orally, but there is an extensive first-pass effect, so that about 20% enters the systemic circulation. The incidence of side effects in patients receiving verapamil is 9-10%; about 1% require discontinuation of therapy. Verapamil is contraindicated in patients with sinus-node disease, unstable atrioventricular block, and shock. Nifedipine has proven useful for hypertension, coronary-artery spasm, and exertional angina; it has little negative inotropic effect. Approximately 90% of an oral dose is absorbed, and 65-70% reaches the systemic circulation after first-pass metabolism. Protein binding of nifedipine ranges from 92 to 98%. Side effects of nifedipine, usually associated with the peripheral vasodilatory action, occur in approximately 15% of patients, requiring discontinuance in 2-5%. Diltiazem hydrochloride has been shown effective in the treatment of coronary-artery spasm; limited studies indicate it may be useful in treating exertional angina, hypertension, and possibly arrhythmias. Diltiazem's oral bioavailability is good (90% reaches systemic circulation), but there is significant interindividual variability between administered dose and resulting plasma concentration. Geriatric patients have delayed absorption and reduced clearance of diltiazem given in sustained-release tablets. Studies of diltiazem are limited at this time. The exact role of calcium-channel blocking agents has not yet been elucidated. However, their ability to influence the calcium channel greatly expands the therapeutic armamentarium for cardiovascular disease and other disorders.

Adolescent↗