The development of reliable compliance tests for antihypertensive drugs.

Many tests for measuring compliance have been proposed, but in most cases compliance rates have been determined without taking into account the factors influencing the interval during which a drug can be detected by a qualitative test after having been taken by the patient. The drug half-life, often used for determining the time at which the sample is collected, is inadequate for obtaining conclusive test results. A procedure is described for the determination of urine collection intervals during which reliable information on compliance can be obtained, using oxprenolol, hydrochlorothiazide, and pindolol as examples.