Article date: September 1990
By: E Hardy, S Kumar, S Peaker, M Feely, T Pullar, in Volume 30, Issue 3, pages 437-441
1. Although, long half‐life compounds appear to be more appropriate pharmacological indicators of compliance with treatment, short half‐ life markers or measurements of short half‐life therapeutic drugs are frequently used. 2. We have compared the usefulness of low‐dose phenobarbitone (a long half‐life indicator), low dose isoniazid (a short half‐life marker) and controlled release metoprolol (Metros) (a controlled release formulation of a short half‐life ‘therapeutic’ drug) in seven volunteers with simulated partial (two thirds) compliance. 3. Detection of isoniazid metabolites in urine had an 83% sensitivity and 94% specificity for detecting ingestion within the previous 24 h and 100% sensitivity and 82% specificity for detecting ingestion within the past 6 h but gave no indication of the longer term pattern of compliance. 4. At 28 days (a time when steady‐state would be obtained for all three drugs) phenobarbitone plasma levels were 70% (66‐76%)‐ median and interquartile range‐of the expected steady‐state level if compliance had been complete. Corresponding figures for metoprolol were 82% (37‐100%). 5. Measurement of phenobarbitone was much superior to isoniazid or metoprolol measurements in reflecting partial compliance over the previous 1 to 4 weeks.
DOI: 10.1111/j.1365-2125.1990.tb03795.x
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