A patient who is nonadherent may suffer drug toxicity if the drug is restarted.
Scenarios:
(1) noncompliance followed by enforced compliance (see below)
(2) taking a much higher dose in an attempt to compensate for skipped doses
(3) restarting a drug dosed for tolerance after a period of noncompliance (seen with heroin users who get out of jail and go back to their previous usage levels)
Sequence for noncompliance followed by enforced compliance:
(1) A patient is noncompliant to a medication.
(2) Seeing that the patient has not responded, the clinician raises the dose without considering noncompliance. The clinician may suspect hypermetabolism without verifying.
(3) The patient is suddenly made compliant (in prison, in the hospital, etc) with the current prescription dose being much higher than it should be.
Risk factors:
(1) The drug has a narrow therapeutic range.
(2) Tolerance occurs during repeated use.
(3) The interrupted drug affects metabolism of another drug.
