Pharmacological treatment of patients with MS : A retrospective study with focus on treatment with AEDs and polytherapy with other CNS active drugs

MS patients are often suffering from chronic pain. Pain is a debilitating symptom and treatment is associated with undesirable adverse reactions, especially long-term treatment where tolerance and dependence issues are concerning. Therefore, antiepileptic drugs are frequently being used in the management of chronic pain. Antiepileptic drugs are among the most susceptible drugs to be involved in pharmacokinetic as well as pharmacodynamic interactions. MS patients often use several different types of CNS-active drugs, yet little research has been done to highlight potential polypharmacy issues. The aim of this study was to investigate the pharmacological treatment of MS patients at the rehabilitation centre for MS, Hakadal, Norway, with regards to current knowledge on polypharmacy, with particular focus on antiepileptic drugs. Medical records from 2009 to 2011 were reviewed and an overview of drug dosages and combinations used by patients at MSSH was created. The present study demonstrated that one third of MS patients used either an AED (antiepileptic drug) or TCA (tricyclic antidepressant) and that one fifth used two or more. There was no difference in age, gender or degree of disability of the patients using these drugs. Polytherapy was widespread, with up to 19 concomitant drugs in use. Although the AEDs are well-known for their pharmacokinetic interactions, this is not of particular concern for MS patients since they mainly used newer AEDs (pregabalin and gabapentin) with little propensity to interact. Pharmacodynamic interactions are of greater concern since more than half of the patients used an opioid, a benzodiazepine or baclofen in addition to their AED/TCA therapy. One third of the patients were elderly and careful considerations regarding pharmacokinetics and possible excessive adverse reactions are of importance. More focus on individualisation of treatment by implementation of therapeutic drug monitoring of AEDs and TCAs and attention to potential pharmacodynamics interactions may be further treatment concerns