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. 1969 Dec 27;4(5686):764–768. doi: 10.1136/bmj.4.5686.764

Steady-state plasma levels of nortriptyline in twins: Influence of genetic factors and drug therapy

Balzar Alexanderson, David A Price Evans, Folke Sjöqvist
PMCID: PMC1630282  PMID: 5391106

Abstract

Nineteen identical (monozygotic) and 20 fraternal (dizygotic) sets of twins between 45 and 51 years of age were given nortriptyline orally in doses of 0·2 mg./kg. body weight three times daily for eight days. The steady-state plasma concentrations of nortriptyline were calculated from the mean of the determinations for days 6, 7, and 8. Identical twins, not treated with other drugs, achieved similar steady-state plasma concentrations of nortriptyline in contrast to fraternal twins who were not given other drugs. The intrapair similarity in steady-state plasma concentrations was not found in identical twins simultaneously treated with various drugs during the experiment. Identical and fraternal twins treated with drugs containing barbiturates had considerably lower steady-state plasma concentrations of nortriptyline compared with untreated twins.

It is concluded that most of the variability in nor-triptyline steady-state plasma concentration between persons who have not received drugs is genetically determined. Exposure to other drugs also influences the steady-state plasma concentration of nortriptyline, which in a given patient may therefore be determined by a resultant of genetic and environmental factors.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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