PubMed Health⌕ Search

Biomedical subjects

A J Atkinson

Publications and source records attributed to A J Atkinson.

At least 91 records · Page 5Linked to original sources
PubMed1975

Pharmacokinetics and metabolism of lidocaine in patients with renal failure.

The kinetics of distribution and elimination of lidocaine and two of its metabolites, monoethylglycinexylidide (MEGX) and glycinexylidide (GX), were studied in 4 uremic patients on chronic hemodialysis. Each patient received a loading dose of 75 mg of lidocaine, followed by a 30 mug/kh/min lidocaine infusion. No toxic side effects from lidocaine were seen during the study. Average values for lidocaine steady-state plasma levels (2.3 mug/ml) clearance (12.3 ml/min/kg), terminal half-life (148 min), and total volume of distribution (1.9 L/kg) were found, and are similar to those values reported for normal subjects MFGX and after lidocaine infusion averaged 1/5-2/3 of the corresponding lidocaine level, as in nonuremic subjects, and plateaued by 6-8 hr. GX levels did not reach plateau by 12 hr and remained relatively unchanged after infusion. It is concluded that lidocaine infusion in uremic patients is safe, with no abnormal cumulation of lidocaine or MEGX. GX levels, however, may increase progressively, even after 12 hr.

Computers↗
PubMed1975

Absolute bioavailability in man of N-acetylprocainamide determined by a novel stable isotope method.

Absorption of a single oral dose of N-acetylprocainamide (NAPA) was studied in 3 normal subjects. Approximately 85% of the oral dose was absorbed and peak plasma NAPA concentrations were reached in 45 to 90 min. In 2 subjects, NAPA was absorbed at a fast initial rate, then more slowly, prolonging the apparent elimination phase half-life. Absolute bioavailability was determined by a new stable isotope method that entailed intravenous injection of NAPA 13C at the same time that an unlabeled NAPA capsule was given orally. Plasma levels and urine excretion of both compounds were determined by mass fragmentography. Bioavailability was assessed by deconvoluting the plasma level vs time curves resulting from intravenous and oral drug administration, and also by comparing the relative percentage of NAPA and NAPA-13C excreted unchanged in the 24 hr after simultaneous administration.

Adult↗
PubMed1970

The effect of diphenylhydantoin on thyroxine metabolism in man.

The effect of 5,5'-diphenylhydantoin on thyroxine metabolism was examined in five normal volunteers. Intravenous injection of radiothyroxine was followed by a 10-12 day control and subsequent 9-14 day treatment periods. During oral administration of diphenylhydantoin, plasma thyroxine concentration decreased to about 80% of its pretreatment level and the plasma radiothyroxine disappearance rate increased a maximum of 20% over control estimates. These changes were a result of increases in both urinary and fecal excretion of radioisotope.A minimum plasma thyroxine was apparent after 10-12 days of diphenylhydantoin administration. In two of the subjects, treatment was sufficiently prolonged to achieve this new steady state. In these subjects, the decrease in total body thyroxine was balanced by the increase in the fractional turnover rate. As a result, absolute thyroxine degradation during diphenylhydantoin administration was unchanged from the pretreatment values. Plasma ultrafiltration was used to estimate the free thyroxine fraction at regular intervals during the control and treatment periods. During diphenylhydantoin treatment, there was little or no change in this fraction and therefore, absolute free thyroxine decreased. Thyroxine-binding globulin and thyroxine-binding prealbumin capacities remained constant. These results indicate that thyroxine degradation can proceed at a normal rate in subjects receiving diphenylhydantoin despite decreases in plasma free thyroxine concentration. If free thyroxine is the only portion of the hormone available for cellular utilization, then free thyroxine clearance must be increased in these subjects. This increase in clearance could represent either a direct stimulation of peripheral thyroxine metabolism by diphenylhydantoin, or it could reflect the response of intrinsic regulatory systems to a diphenylhydantoin-mediated displacement of thyroxine from thyroxine-binding globulin. Whatever the mechanism for this effect, a decreased free thyroxine value in patients receiving diphenylhydantoin may not imply hypothyroidism.

Adult↗