Drug exposure and the risk of multiple sclerosis: A systematic review.

BACKGROUND: Several environmental and lifestyle factors have been associated with multiple sclerosis (MS) risk, including some pharmacological treatments. We systematically reviewed the literature on prescription drug exposure and MS risk.

METHODS: Six databases were searched for original observational studies reporting drug exposure and MS risk published before 2017.

RESULTS: Thirteen articles fulfilled inclusion criteria. Exposure to neither amiloride nor valproic acid was associated with MS (adjusted hazard ratio (adj.HR = 1.34;95% CI:0.81-2.20; adj.HR = 1.30;95%CI:0.44-3.80, respectively). Four studies explored oral contraceptive exposure and reported no association with MS; while a single study found an increased risk (odds ratio [adj.OR] = 1.52;95%CI:1.21-1.91). While penicillin exposure was associated with reduced risk of developing MS (adj.OR = 0.5;95%CI:0.3-0.9), a later study observed an elevated risk for penicillin (adj.OR = 1.21;95%CI:1.10-1.27) and all antibiotics (adj.OR = 1.41;95%CI:1.29-1.53), which was potentially attributed to underlying infection. Anti-tumor necrosis factor-alpha (TNFα) was not associated with MS risk in persons with inflammatory bowel disease (standard morbidity ratio = 4.2;95%CI:0.1-23.0) and arthritis (standardized incidence ratio = 1.38;95%CI:0.69-2.77); however, men exposed to anti-TNFα who also had arthritis and individuals with ankylosing spondylitis were at an increased risk (standardized incidence ratios = 3.91;95%CI:1.47-10.42 and 3.48;95%CI:1.45-8.37, respectively). A reduced risk of MS was observed with exposure to the beta2-adrenergic agonist fenoterol (adj.OR = 0.58;95%CI:0.45-0.76), and the sedating histamine 1-receptor antagonists (adj.OR = 0.2;95%CI:0.1-0.8), but not the non-sedating equivalent (adj.OR = 0.8;95%CI:0.4-1.6).

CONCLUSIONS: The suggestion that some drugs may prevent MS is intriguing and warrants further study. In addition, further pharmacovigilance is needed to assess the safety of anti-TNFα drugs in specific populations in the context of MS risk.