Statistician Department of Epidemiology, Lazio Regional Health Service, Rome Roma, Italy
Background: Myasthenia gravis (MG) is an autoimmune disorder treated with several non-specific drugs. In the context of a comparative study of efficacy and safety of drugs used in rare neuromuscular and neurodegenerative diseases (CAESAR - call AIFA_FV_2012-13-14), we assessed the patterns of use of drugs in MG.
Objectives: To assess the use of pyridostigmine (Py) in the presence of potential contraindications and the use of potentially contraindicated drugs in MG.
Methods: A retrospective cohort study on MG patients was conducted based on administrative healthcare data of the Italian regions Latium, Tuscany and Umbria. For a cohort of Py users, potential contraindications (mechanical gastrointestinal/urinary obstruction, obstructive respiratory diseases, cardiovascular diseases, mechanical ventilation) in the two years before the first prescription of Py and determinants of its use were evaluated. Among MG patients, use of drugs with potential contraindications (drugs for the cardiovascular system, for the nervous system, immunosuppressants) in the first year after enrolment and determinants of their use were evaluated.
Results: We included 2,369 patients with MG for Latium, Tuscany and Umbria in the period 2013-2019. In the first year of follow-up, we observed a prevalent Py use of 60.0%, 62.2% and 55.8%, respectively. Py use was mainly combined with azathioprine and vitamin D (24.4%, 41.5% and 22.1% respectively). Among 591 incident Py users (22.0% in Latium, 25.9% in Tuscany and 33.3% in Umbria), presence of contraindications was observed for 14.3%, 15.7% and 17.4% of patients, respectively. Previous comorbidities and complications, increasing age, and mechanical ventilation were found to be determinants of the potentially contraindicated Py use. 67.0% of MG patients in Latium, 59.0% in Tuscany and 57.6% in Umbria used potentially contraindicated drugs. Female sex (for Tuscany only), previous comorbidities, polypharmacy, and increasing age were found to be related to potentially contraindicated drug use.
Conclusions: Both the high use of potentially contraindicated Py and of potentially contraindicated non-specific drugs in MG can be partially explained by increasing age and presence of comorbidities and complications.