Intended for healthcare professionals


Reconsidering the scope of US state laws allowing pharmacist substitution of generic drugs

BMJ 2020; 369 doi: (Published 23 June 2020) Cite this as: BMJ 2020;369:m2236
  1. Jonathan J Darrow, assistant professor,
  2. Jessica E Chong, research associate,
  3. Aaron S Kesselheim, professor
  1. Program on Regulation, Therapeutics, and Law (PORTAL), Division of Pharmacoepidemiology and Pharmacoeconomics, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, USA
  1. Correspondence to: J J Darrow

Despite high rates of generic prescribing, branded medicines still account for most drug costs. Amending the law to provide pharmacists with greater authority to substitute clinically similar alternatives has the potential to cut spending, say Jonathan Darrow and colleagues

The generic fill rate has reached 90% in the US, representing one of the great success stories of government and payer policy and the international generic drug industry. Nevertheless, mean expenditures on prescription drugs continue to increase. They now exceed $1000 (£790; €880) per person per year, higher than in Europe, where generic prescription rates range from 17% to 83%.1 This paradox is partly explained by the rising prices of the 10% of prescriptions that are for brand name medications (other causes include increased overall prescription volume and, in some drug markets, high generic prices). Although some new drugs represent therapeutic breakthroughs, most represent incremental advances and many are clinically equivalent—or occasionally inferior—to existing medicines.23 Part of the costliest 10% of prescriptions therefore could be avoided by using cheaper alternatives.

Although prescribers may exercise discretion to choose cheaper alternatives, substitution could also be initiated by pharmacists, who generally have better information about product supply, insurance formularies, and patient co-payments. Current US laws, however, generally allow pharmacist substitution only when the alternative product is designated by the Food and Drug Administration as virtually identical to the branded version. One way of lowering drug costs is to provide pharmacists with greater latitude to apply their professional expertise to select among clinically interchangeable medicines.

US drug substitution law

In the US, state laws define the scope of pharmacist substitution but are largely based on the FDA’s determination of bioequivalence, defined by the 1984 Hatch-Waxman Act as the absence of a significant difference in pharmacokinetic and pharmacodynamic properties. A substitutable drug must also be pharmaceutically equivalent, …

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