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Biomedical subjects

R A Long

Publications and source records attributed to R A Long.

41 records · Page 3Linked to original sources
PubMedDate not supplied

Bioavailability of organic nitrates: a comparison of methods for evaluating plethysmographic responses.

Erythrityl tetranitrate, a long-acting organic nitrate, was compared with isosorbide dinitrate in a double-blind, placebo-controlled complete crossover study in 15 healthy male volunteers. A digital plethysmogram and ear densitogram were used to assess the physiologic response to these two sublingual nitrates, with the intensity and duration of drug effect calculated by differences in diastolic amplitude intensity before and after drug administration. Both 5 mg sublingual erythrityl tetranitrate and 5 mg isosorbide dinitrate produced significant increases in diastolic amplitude intensity for up to 3 hours. The erythrityl tetranitrate peak effect was less than that of the isosorbide dinitrate, but the incidence of headaches was also less. The ear densitogram was found to be an effective means of assessing the diastolic amplitude intensity changes.

Adult↗
PubMedDate not supplied

A steady-state evaluation of the effects of propantheline bromide and cholestyramine on the bioavailability of digoxin when administered as tablets or capsules.

Drug interactions can profoundly alter the absorption of digoxin in tablet form. This study evaluated whether digoxin solution in capsules, a new dosage form with 90% to 100% bioavailability, would reduce such alterations, specifically those caused by cholestyramine and propantheline bromide. The investigation used a six-treatment, steady-state, balanced, incomplete block design with 18 healthy adults studied for four continuous two-week treatment periods. Treatments were either two 0.25 mg digoxin tablets or two 0.20 mg digoxin capsules administered alone, with propantheline, 15 mg qid, or with cholestyramine, 8 g qd. Bioavailability was determined from steady-state, 24-hour area under the serum concentration-time curve (AUC, ng X h/mL) and from 0- and 24-hour trough serum digoxin concentrations (ng/mL). The AUCs for tablets alone, with cholestyramine, and with propantheline were 32.8 +/- 13.3 (+/- SD), 22.4 +/- 12.1, and 40.6 +/- 13.9, respectively, while corresponding values for capsules were 31.7 +/- 9.3, 24.7 +/- 7.9, and 35.9 +/- 12.8. The trough concentrations for tablets alone, with cholestyramine, and with propantheline were 0.88 +/- 0.47, 0.61 +/- 0.38, and 1.09 +/- 0.35, respectively; trough concentrations for capsules were 0.77 +/- 0.28, 0.74 +/- 0.28, and 0.96 +/- 0.48, respectively. The only significant differences in AUC were seen when comparing tablets alone versus tablets with cholestyramine (P less than .0005) and tablets with propantheline (P less than .01). A significant finding was also observed when comparing trough concentrations for tablets alone versus tablets with cholestyramine (P less than .005).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Erythrityl tetranitrate compared with isosorbide dinitrate. Effects on systolic time intervals and nitrate modification of effects of food.

The pharmacologic effects of erythrityl tetranitrate (ETN) and isosorbide dinitrate (ISDN) were compared to placebo using systolic time intervals (STI) in a randomized, double-blind study in 15 fasted male volunteers. Sublingual doses of ETN 5 mg, ISDN 5 mg, and placebo were administered to each volunteer at weekly intervals, and measurements of heart rate and STI [pre-ejection period (PEP), left ventricular ejection time (LVET), and PEP/LVET ratio] were made serially for up to 6 hours after each dose. STI were determined using ear densitography. Evaluation of the pharmacologic effects of ETN and ISDN were based on placebo-corrected changes from baseline values. Ejection time index (ETI) [LVET corrected for heart rate] was shortened, but the changes were not statistically significant for either drug. However, after ETN and ISDN, statistically significant (p less than 0.05) changes in PEP and PEP/LVET ratio were demonstrated for up to 240 minutes after dosing. Unexpected marked changes in the baseline corrected PEP/LVET ratio were observed following food at 4 hours after dosing. This suggests increased inotropy during the postprandial period.

Adult↗