Prevalence of Contraindicated Medical Conditions and Use of Precluded Medications in Patients with Painful Neuropathic Disorders Prescribed Amitriptyline

Abstract

Amitriptyline is a tricyclic antidepressant that is historically indicated and used to manage depression. More recently, due to clinical evidence demonstrating efficacy, it is often prescribed in the management of painful neuropathic disorders (PNDs). However, the amitriptyline label contains numerous preclusions (contraindications, warnings/precautions, drug interactions). Our objective was to measure the frequency of amitriptyline prescriptions in PND patients using the U.K. General Practice Research Database and assess whether any prescriptions were given to patients with preclusions listed in the product label. We identified a total of 13,546 patients (mean age 59 +/- 16.2 years; 66.7% female) who had a diagnosis of a PND and received > or =1 prescription for amitriptyline between July 1998 and June 2001. Nearly half (46.7%) of PND patients prescribed amitriptyline had > or =1 preclusion for its use; 3.5% had > or =1 contraindication; 22% had > or =1 warning/precaution; and 33% received > or =1 medication with a potential for drug interactions with amitriptyline. Preclusions were more likely in women than in men (48.3% vs. 43.4%, P < 0.0001); their incidence increased with age (42.8%, 50.4%, 55.1%, and 52.3% among those ages <65, 65-74, 75-84, and 85+ years, P < 0.0001), and the number of patients with preclusions was the highest in the phantom limb pain group (67.4%) and lowest in the atypical facial pain group (42.9%), P < 0.001. The average daily amitriptyline doses (starting: 33.6 +/- 32.4 mg; maintenance: 42.1 +/- 39.9 mg) were low compared to those used for the treatment of depression. Results indicate that, in a significant number of cases, the existence of preclusions did not prevent the prescribing of amitriptyline. Our findings raise a potential concern about the way this medication is being used. However, the clinical significance of these data is, as yet, unclear. Although, in theory, adverse outcomes may have been associated with this practice, we could not confirm this with this database analysis.