Influence of route of administration on physiological availability of levodopa in dogs

Dosage form Design for Improvement of Bioavailability of Levodopa II: Bioavailability of Marketed Levodopa Preparations in Dogs and Parkinsonian Patients

“…Both results seem to be consistent considering that the data of Coutinho et al (10) involved total radioactivity measurements. The profile of plasma levodopa levels and the pattern of urinary excretion obtained in this experiment following oral administration of levodopa, respectively, agree with the results and the observations reported previously (10)(11)(12). In the urine, 44-57s of the oral dose was excreted, including metabolites, but only small amounts of intact levodopa were excreted.…”

“…The plasma concentration-time curves and the estimated pharmacokinetic parameters obtained in these studies compare well with the data obtained by Coutinho et al (10) and Colter et al (11) following intravenous administration of radiolabeled levodopa to dogs. However, Coutinho et al (10) reported that -75% of the intravenously administered dose, in terms of total radioactivity, was recovered in the urine within 72 hr.…”

Bioavailability and Pharmacokinetics of Oral Dopamine in Dogs

“…Animal Experiment-Intravenous Administration-An aqueous solution of 10 mg of DA was administered intravenously to dogs and blood samples were withdrawn a t 0, 2.5, 5,10,15,20,30,45, and 60 min after administration. A dose of DA-S04 or DOPAC equivalent to 10 mg of DA was administered intravenously to dogs and blood samples were withdrawn periodically.…”

Lipid synthesis inhibitors: Effect on epidermal lipid conformational changes and percutaneous permeation of levodopa

“…Treatment given to various groups, each consisting of 5 rats can be summarized as follows: Group 1: normal skin + LD + carbidopa (16 mg); Group 2: ethanol perturbation + AVN (750 µg) + Blood samples (0.25 mL) were withdrawn from tail veins of rats after specified time intervals and centrifuged at 2500 rpm for 10 minutes at 4°C. The plasma was analyzed or intact LD by the method reported by Cotler et al 22 Briefly, the deproteinized plasma (0.2 mL) was added to 1.0 mL of edetic acid solution (20 mg/mL). Water (1.0 mL) and 2 drops of ethanolic solution of naphthoresorcinol (2% wt/vol) were added, and the specimen was mixed.…”