The clinical impact of reported variance in potency of antipsychotic agents

There is significant disagreement on the clinical equivalence (or potency) of antipsychotic agents, with up to 500% variance reported in texts. To address the extent and consequences of these discrepancies, we took a random sample of 18 common psychiatry, psychopharmacology and pharmacology texts for antipsychotic equivalence tables. We found a marked variation in stated equivalences for the majority of antipsychotics. Most affected were the high potency (haloperidol, fluphenazine) and newer (molindone) drugs, which had a 500% variance. This variation inadvertently contributes to the misuse of these agents. For instance, high-potency antipsychotics are prescribed in far larger doses than necessary, leading to decreased efficacy and increased side effects. Steps to simplify and rationalize the use of these agents are recommended.