Single Versus Multiple Dose Ivermectin Regimen in Onchocerciasis-infected Persons with Epilepsy Treated with Phenobarbital: A Randomized Clinical Trial in the Democratic Republic of Congo

Background: There is anecdotal evidence that ivermectin may decrease the frequency of seizures in Onchocerca volvulus-infected persons with epilepsy (PWE). Methods In October 2017, a 12-month clinical trial was initiated in rural Democratic Republic of Congo. PWE with onchocerciasis-associated epilepsy with ≥2 seizures/month were randomly allocated to receive over a one year period, ivermectin once or thrice (group 1), while other onchocerciasis-infected PWE (OIPWE) were randomized to ivermectin twice or thrice (group 2). All participants also received anti-epileptic drugs (AED). Study outcomes included seizure freedom during the last four months (primary endpoint), decrease in microfilarial density, and occurrence of adverse events. A multiple logistic regression model was used to evaluate the primary outcome. Results Of the 197 OIPWE enrolled, 100 were randomized to receive ivermectin thrice, 52 twice, and 45 once. In an intent-to-treat combined analysis of data from group 1 and 2, the probability to become seizure-free for OIPWE treated with ivermectin twice per year was significantly higher than in those treated once (OR: 5.087, 95% CI: 1.378-19.749; p=0.018) and individuals who received ivermectin twice had a 4.471 (95% CI: 0.944-6.769, p=0.075) times higher odds of seizure freedom than those received ivermectin once per year. Absence of microfilariae during the last 4 months was associated with a higher probability of seizure freedom (p=0.027). Conclusions Increasing the number of ivermectin treatments per year was found to suppress both microfilarial density and seizure frequency in OIPWE, suggesting that O. volvulus infection plays an etiological role in causing seizures. Registration: www.clinicaltrials.gov; NCT03852303