Relationship Between Adherence Rate Threshold and Drug 'Forgiveness'.

Area of Science:

• Pharmacology
• Pharmaceutics
• Drug Safety

Background:

• Medication adherence rate (A) is the proportion of prescribed doses taken.
• A therapeutic effect is often assumed to be maintained above an adherence rate threshold (A_th).
• Drug forgiveness (F) is the number of consecutive missed doses that still allow for therapeutic effect.

Purpose of the Study:

• To define the relationship between medication adherence rate (A), adherence threshold (A_th), and drug forgiveness (F).
• To investigate the implications of drug forgiveness on maintaining therapeutic drug effects.
• To determine if a universal adherence threshold (A_th) exists for all medications.

Main Methods:

• Formulated the relationship between A_th, F, and the number of days (N) for a once-daily drug: A_th = (N - F)/N.
• Analyzed the probability of maintaining therapeutic effect at adherence rates below A_th.
• Considered drug forgiveness (F) as a function of drug effect duration (D) and pharmacokinetic/pharmacodynamic properties.

Main Results:

• Established a mathematical relationship between adherence rate threshold (A_th) and drug forgiveness (F).
• Demonstrated that maintaining therapeutic effect depends on avoiding more than F consecutive missed doses.
• Showed that the probability of therapeutic effect is linked to adherence rates below A_th.

Conclusions:

• Drug forgiveness (F) is a critical factor influencing the required medication adherence rate (A).
• A universal adherence threshold (A_th) is not applicable to all drugs due to varying drug effect durations (D).
• Pharmacokinetic and pharmacodynamic properties significantly impact drug forgiveness and thus adherence thresholds.