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Biomedical subjects

M Mayersohn

Publications and source records attributed to M Mayersohn.

At least 109 records · Page 6Linked to original sources
PubMed1979

Digoxin-quinidine interaction Pharmacokinetic evaluation.

Several recent reports have shown that plasma concentrations of digoxin increase when quinidine is administered along with digoxin; the present study was designed to explore the pharmacokinetics of this digoxin-quinidine interaction in six subjects. The elimination half-life of digoxin, although variable, did not change appreciably (42 vs. 44 hours) when quinidine was administered. Other pharmacokinetic values were substantially reduced in the presence of quinidine: total body clearance (from 3.08 to 1.96 ml per minute per kilogram), renal clearance (from 1.64 to 1.09 ml per minute per kilogram) and volume of distribution (from 10.87 to 7.35 liters per kilogram). The results may be explained by the displacement of digoxin from binding sites in tissue by quinidine, causing a rise in the plasma concentration of digoxin. The reduction in renal clearance of digoxin may result also from inhibition of renal secretion of digoxin by quinidine.

Digoxin↗
PubMed1978

Dose tolerance and pharmacokinetic studies of L (+) pseudoephedrine capsules in man.

Dose tolerance and pharmacokinetic studies of pseudoephedrine sustained action capsules were performed in thirty-three adult male subjects who received either 120 mg or 150 mg capsules every twelve hours for seven consecutive days in a double-blind parallel design study. Although only one subject in the 150 mg group was discontinued prematurely from this study, a large number of side effects typical of CNS stimulation were seen. A placebo effect might account for a portion of these complaints, however symptoms evaluated as being due to drug were significantly more severe and persistent in the 150 mg group. Pulse rates showed a persistent and significant increase while systolic and diastolic blood pressure fell from the baseline values in both groups. A pharmacokinetic analysis of the pseudoephedrine plasma concentration-time data provided estimates of half-life and the volume of distribution/availability ratio. The values obtained were in good agreement with values reported by others. Half-life was not influenced by urine pH probably as a result of the narrow range of urine pHs observed in the subjects. Calculations of relative bioavailability suggest that the 120 mg capsule formulation has a 30% greater bioavailability compared to the 150 mg capsule.

Adult↗
PubMed1978

Relationship between plasma concentration and dose of digoxin in patients with and without renal impairment.

The purpose of this study was to determine if there is a linear relationship between oral doses of digoxin and various measurements of steady-state digoxin plasma concentration and urinary excretion in patients with wide range of renal function. Ten patients (mean age 58 years) with creatinine clearances greater than 50 ml/min/1.73 m2 BSA (mean creatinine clearance 80 ml/min/1.73 m2 BSA) and nine patients mean age 61 years) with creatinine clearances less than 50 ml/min/1.73 m2 BSA (mean creatinine clearance 20 ml/min/1.73 m2 BSA) were given digoxin tablets orally at two or three different dose levels (dose range 0.0313--0.5 mg/day). After a dosing period equal to at least five half-lives, three to four consecutive daily digoxin plasma concentrations were determined. Plasma concentrations and urinary digoxin excretion were measured during one 24-hour dosing interval at each dose level. Digoxin plasma and urine concentrations were determined in triplicate using radioimmunoassay. Individual patient plots provided evidence of linearity for: digoxin 24-hour steady-state plasma concentration vs dose; digoxin 24-hour cumulative urinary excretion versus dose; and area under the digoxin plasma concentration-time curve during a 24-hour dosing interval vs dose. Absolute values for these various parameters indicated substantial interpatient variation probably due to patient differences in both digoxin absorption and digoxin total body clearance. These results indicate that there is a linear relationship between digoxin plasma concentration and dose in patients with normal and decreased renal function. This linearity is support for dose-independent pharmacokinetics of digoxin in man. We conclude from these data that a change in digoxin dose should result in a proportional change in digoxin plasma concentration over the dose range examined.

Administration, Oral↗
PubMed1978

Digoxin disposition kinetics in dogs before and during azotemia.

The purpose of this study was to evaluate the disposition kinetics of digoxin after the administration of a single intravenous dose to the same dogs before and during azotemia. The digoxin plasma concentration-time data were fitted to a multicompartment model using nonlinear regression analysis. During azotemia, the biological half-life of digoxin was prolonged in six of seven dogs, while digoxin renal clearance, body clearance and apparent volume of distribution were significantly decreased. There was a corresponding increase in the apparent volume of the "central" compartment of digoxin. Approximately 45% of a digoxin dose was excreted by the kidney in these animals indicating a substantial nonrenal component to digoxin elimination in the dog. This nonrenal elimination did not change during azotemia, despite a decrease in renal clearance by 61%.

Animals↗
PubMed1978

Kinetics of pharmacologic response to cocaine.

Cocaine plasma concentration-response-time data obtained from the literature were analyzed by pharmacokinetic methods. The plasma concentration-time data yield an elimination half-life of approximately 1 hour and the data suggest that only about 20% of an oral dose of cocaine is absorbed intact into the systemic circulation. Response, as assessed by means of a relative "high" rating scale, declined linearly with time as predicted by theory. The rate of decline of response was found to be 0.0221 "high"/min. The rate of decline of response is a function of the apparent first-order elimination rate constant (K) of the drug and the slope of the response-log plasma concentration curve (m). A value for m of 4.2 "high" was calculated from the response-time data which agreed well with a value of 3.9 "high" for m determined from the slope of the response-log plasma concentration curve.

Cocaine↗
PubMed1977

Aspirin.

Explore the source record for details and available documents.

Aspirin↗
PubMed1977

Evaluation of a charcoal-sorbitol mixture as an antidote for oral aspirin overdose.

The preparation of charcoal in a 70% sorbitol solution results in a suspension that is more palatable and less gritty than an aqueous slurry of charcoal. Although the charcoal-sorbitol mixture may be slightly less effective in reducing the extent of aspirin absorption compared with a charcoal slurry, it may prove to be of particular value in those cases where acceptance of a charcoal slurry presents a problem.

Adult↗
PubMed1977

The rapid reduction of disulfiram in blood and plasma.

A gas chromatographic assay procedure was developed to quantitate the reduction product of disulfiram, diethyldithiocarbamate (DDC), in blood and plasma. The procedure involved the in situ methylation of DDC prior to the extraction and chromatography of the methyl ester. The minimal sensitivity achieved was 0.2 microgram/ml from 1 ml of blood or plasma. The coefficient of variation about any concentration was 10.5%. Calibration curves having a reproducible nonlinear form were prepared up to 9 microgram/ml. The assay procedure was used to evaluate the stability of disulfiram and DDC in blood. Disulfiram was rapidly and quantitatively reduced to DDC within 4 minutes. The DDC thus formed decomposed in human and dog blood with half-lives of 70 and 100 minutes, respectively. The implications of these findings are discussed with respect to the chemical form of disulfiram responsible for the ethanol-sensitizing effect.

Animals↗
PubMed1976

Disposition kinetics of two oral forms of quinidine.

There are relatively few studies on the disposition properties of quinidine. We have studied in 10 normal subjects conventional quinidine sulfate and a slow-release quinidine bisulfate. Single and repetitive doses were given; blood and urine concentrations were measured by the method of Cramer and Isaakson. After a single dose of two tablets of quinidine sulfate (400 mg), the average peak concentration was 2.13 +/-0.22 mug/ml (+/-SEM); following two tablets of the slow-release form, the average peak concentration was 1.17 +/-0.12 mug/ml. T-max was approximately 2 hr with quinidine sulfate and 4 hr with quinidine bisulfate. One fourth of both forms of the drug was recovered in the urine. Total body clearance was 0.36 L/kg-hr and renal clearance was 117 +/-22ml/min for both. With multiple dosing the serum quinidine concentration was higher than these predicted from the results of the single-dose study. Based on the mean estimates of quinidine half-life of 6 hr, a rapid method for achieving steady-state levels of quinidine would be to give an initial dose twice that of the maintenance dose. With the slow-release product if an equivalent dose was given every 12 hr, the mean steady-state quinidine serum concentration would be approximately the same.

Adult↗
PubMed1973

Relative bioavailability of commercial ampicillin formulations in man.

The relative bioavailability of three commercial ampicillin products was examined in 12 human subjects using a crossover experimental design. Based upon the areas under the ampicillin plasma concentration-time curves after the oral administration of 250 mg. ampicillin and using an analysis of variance technique no statistically significant differences were found between the products examined. These findings are in contrast to those of a recent report and appear to be explained by formulation differences. These relatively minor differences in formulation reflect the importance of formulation variables in providing efficient drug therapy. The intrasubject variation associated with several of these products is quite marked and is consistent with the incomplete and erratic absorption of this antibiotic in man.

Administration, Oral↗