The dose that was halved

A clinic halved the dose of a drug for one group of patients and the results were indistinguishable from the full dose. The finding saved money. It also raised a question nobody had asked for forty years.

Many standard doses were set early in a drug's life, in small trials designed to find a level that worked rather than the lowest level that worked. Once a figure enters a formulary it is copied forward, and there is rarely anyone with a reason to test downwards. Manufacturers do not benefit. Regulators approve what is submitted. Prescribers follow the label, correctly, because departing from it transfers risk to them.

Dose-finding studies that run in both directions have found reductions possible in a surprising number of cases, with fewer side effects and better adherence, since many people stop taking a drug because of how it makes them feel rather than because they think it has stopped working. They have also found the opposite: doses too low for part of the population, usually because the original trial under-represented people with a different body mass or a different liver enzyme profile.

Neither result is an argument for patients adjusting their own doses, which remains a reliable way to make an illness worse. It is an argument about where research effort goes. A trial that lowers a dose has no commercial sponsor, so it happens only if a public body funds it, and public bodies fund it only if someone has noticed the question.

The clinic's result changed one line in one guideline. The more useful outcome was a standing item on an agenda: for each drug in routine use, when was its dose last tested, and in whom.