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Biomedical subjects

R Lehtovaara

Publications and source records attributed to R Lehtovaara.

7 recordsLinked to original sources
PubMed1979

Antipyretic analgesics in patients on antiepileptic drug therapy.

The effect of administration for three days of acetylsalicylic acid (1500 mg/day), phenylbutazone (300 mg/day), paracetamol (1500 mg/day) and tolfenamic acid (300 mg/day) on serum concentrations of phenytoin and carbamazepine were studied in a group of patients on continuous antiepileptic therapy. When measured 10 h after the last dose of the analgesics, the only significant effect was a decrease in total serum phenytoin after three days of phenylbutazone. When six patients on continuous phenytoin therapy took phenylbutazone for two weeks there was at two days an initial decrease, followed by a signficiant increase in total serum phenytoin and a concomitant increase in free phenytoin in serum. Even phenylbutazone was well tolerated by most of the patients. However, its use had to be discontinued on one patient due to obvious signs of phenytoin intoxication, with concomitant increases in the serum free and total phenytoin concentrations.

Adult↗
PubMed1979

Effect of increased bioavailability of phenytoin tablets on serum phenytoin concentration in epileptic out-patients.

1. The bioavailability of a brand of phenytoin tablets used in Finland was improved in 1976. In the present retrospective study serum concentrations of phenytoin, measured before and after the change of bioavailability, are compared in 50 epileptic out-patients, who for various reasons used exactly the same dose of phenytoin tablets and of other drugs despite the increased bioavailability of phenytoin. 2. The mean increase of serum phenytoin steady-state concentration was about 70% after the change of bioavailability but there were considerable interindividual differences in the response. The mean increase in serum phenytoin was only 28% in patients with serum phenytoin concentrations 5 microgram/ml or less but the mean increase was 100% in patients with serum phenytoin between 5 and 10 microgram/ml. In patients with serum phenytoin concentrations more than 10 microgram/ml the mean increase in concentration was 60-80% after the improvement of bioavailability. However, in these groups of patients some clinically manifested phenytoin intoxications enforced the patients to the control and to dose reduction obviously before the steady-state concentration of phenytoin was reached. 3. On the basis of our experiences and those reported in the literature some proposals are presented to be considered when the bioavailability of phenytoin or of another drug with a narrow therapeutic range and a dose-dependent kinetics has to be changed.

Biological Availability↗
PubMed1975

Effect of antiepileptic drugs on the elimination of various tetracycline derivatives.

Elimination of the bacteriostatics tetracycline, doxycycline, methacycline, oxytetracycline, demethylchlortetracycline and chlortetracycline was studied in healthy control persons and in patients on long-term antiepileptic therapy. The half-life of doxycycline was significantly shorter in patients than in the controls. The half-lives of other tetracycline derivatives and their excretion in urine were not significantly different between the two groups. Accordingly, in order to maintain an adequate serum level of doxycycline it should be given twice daily to patients on long-term therapy with barbiturates, diphenylhydantoin or carbamazepine. The classical tetracycline derivatives studied may be administered according to conventional principles.

Adolescent↗