We Have Enough Variance in Drug Therapeutics—We Don’t Need More

Obtaining a satisfactory clinical response to drug therapy in clinical practice is painstaking, and requires scrupulous monitoring. For example, when initiating warfarin, frequent INR sampling is mandatory, and despite this, a large percentage of patients continue to have variance unexplained by changes in concomitant drug therapy or diet. Drugs like amiodarone are even more challenging because there is no easily measurable surrogate for clinical efficacy, and its unusual pharmacokinetic profile makes patient dose titration almost impossible. Most patients receive the same arbitrary dose of the drug until they have a clinical recurrence, yet the drug’s bioavailability is mightily influenced by a host of factors including food (see reference). Formulation changes (and there are multiple generic versions of amiodarone) just add to the complexity, and place patients at high risk for recurrence of serious, and in some cases, life-threatening arrhythmia.