Amitriptyline tablets reconsidered

Abstract

We recently noted that three different brands of amitriptyline tablets contain different amounts of drug, even though their labels give the same number of milligrams.1 Laroxyl (Roche) and Saroten (Warner) declare the drug content as amitriptyline base, while Tryptizol (MSD) declares it as the hydrochloride. Laroxyl and Saroten tablets thus appear to contain 13% more drug than Tryptizol. Although there is no good evidence that harm has resulted from this confusion, it seems fair to expect manufacturers to agree among themselves to standardize amitriptyline tablets even before a monograph on the drug appears in the British Pharmacopoeia. Unfortunately agreement will be difficult to reach because each company sells the drug in many countries, and no one company first introduced it in all of them. We understand that the BP Commission is at present considering what convention to adopt in expressing the strength of medicaments. Hitherto most BP standards have been expressed in terms of salts, but some newer drugs have been standardised in terms of the therapeutically active portion of the molecule. The latter method seems preferable, particularly when more than one salt of a drug is used.