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Biomedical subjects

R Wyatt

Publications and source records attributed to R Wyatt.

At least 91 records · Page 5Linked to original sources
PubMed1978

Oral theophylline dosage for the management of chronic asthma.

Theophylline dosage requirements to maintain serum concentrations of 10 to 20 microgram/ml among asthmatic patients were examined in 156 children, ages 2 1/2 months to 16 years, and 33 otherwise health adults. Using 100% bioavailable preparations, low doses were used initially and increased, if tolerated, at three-day intervals. Final dosage was based on serum theophylline measurements which were subsequently repeated after six or more months of therapy. Dosage standardized by weight averaged 24.1 +/- 5.5 mg/kg/day (mean +/- SD) among the 77 children under age 9 years. Age-related variability of weight-adjusted doses were not observed for younger children, but average dose requirements decreased progressively beyound age 9 years to 13 mg/kg/day for patients beyoung 16 years of age. Although interpatient variability in dosage was confirmed at all ages, intrapatient variability in requirements over an average eight-month interval were small; dosage changes to maintain therapeutic serum concentration were primarily associated with growth. These data allow age-specific guidelines for dosage recommendations based on the likelihood of optimally effective and potentially toxic serum theophylline concentrations.

Administration, Oral↗
PubMed1978

Guide to oral theophylline therapy for the treatment of chronic asthma.

Theophylline, when used appropriately, seems to be the most effective noncorticosteroid prophylactic medication for chronic asthma. Dosage, however, requires consideration of the relationship between serum concentration, efficacy, and toxicity, in addition to the variability in rates of elimination. Therapy is initiated with 16 mg/kg/day or 400 mg/day (whichever is less) in divided doses at appropriate intervals depending on the rate of absorption of the product used. If side effects are absent, the dosage is increased at three-day intervals until the age-related mean dosage necessary to produce a therapeutic level, is reached. Final dosage adjustment is generally based on a single determination of serum concentration; dosage requirements generally then remain constant for six to 12 months depending upon the child's growth rate. Dosage adjustment in this manner optimizes benefit, minimizes risk of toxic effect, and avoids excessive numbers of serum theophylline measurements.

Administration, Oral↗
PubMed1976

The expression of normal ventricular repolarization in the body surface distribution of T potentials.

Isopotential maps from 120 normal subjects were obtained from 192 simultaneously recorded electrocardiographic leads. Maps were plotted at 1 msec intervals during the QRS and 5 msec intervals during the ST-T deflection. Repetition of QRS features was evident during all but the first few msec of the initial half of serial T maps. This suggests similarities of the normal sequence of ventricular excitation and recovery. Such similarities have been demonstrated by direct studies but are not evident from other electrocardiographic examinations. Serial maps during later portions of the T wave showed decreasing intensity of potentials with little change of body surface locations. This also correlates with an established feature of ventricular repolarization, namely that potential difference boundaries with stable locations are widely distributed during part of that process. Findings suggest isopotential maps show features of ventricular recovery not apparent from less extensive examinations.

Action Potentials↗