L-arginine and aged garlic extract for the prevention of migraine: a study protocol for a randomised, double-blind, placebo-controlled, phase-II trial (LARGE trial)

Abstract

AbstractIntroductionMigraine is a common and distressing neurological condition characterised by recurrent throbbing headaches, nausea and heightened sensitivity to light and sound. Accumulating evidence suggests that cerebral arteries dilate during migraine, causing distal microvessels to constrict, which could activate nociceptors and cause onset of headache pain. If so, preventing or attenuating chronic microvascular constriction, and promoting a dilatory phenotype, may reduce frequency and/or severity of migraines. The primary aim of the L-Arginine and Aged Garlic Extract (LARGE) trial is to investigate whether oral treatment with dietary nutraceuticals, L-arginine and aged garlic extract (AGE), both systemic vasodilatory agents, will alleviate migraine frequency, duration and severity in adults with chronic frequent episodic migraines.Methods and analysisThe study is a randomised double-blind placebo-controlled phase-II single-site clinical trial conducted in Perth, Australia. The target sample is to recruit 240 participants diagnosed with chronic frequent episodic migraines between 18 and 80 years of age. Participants will be randomised to one of four treatment groups for 14 weeks (placebo induction for 2 weeks, followed by 12 weeks on one of the respective treatment arms): placebo, L-arginine, AGE, or a combination of L-arginine and AGE. The doses of L-arginine and AGE are 1.5 g and 1 g daily, respectively. The primary outcome is to assess migraine response using change in migraine frequency and intensity between baseline and 12 weeks. Secondary outcomes include the impact of L-arginine and/or AGE on photosensitivity, retinal vessel changes, and blood biomarker concentrations of vascular tone, following a 12-week intervention.Ethics and disseminationThe Curtin University Human Research Ethics Committee (HREC) has approved this study (Approval number: HRE2020-0466; Version 4; 16thAugust 2021). Written consent will be obtained from all participants prior to commencing their participation in the trial. The results of the study will be disseminated in peer-reviewed publications and presented at key national and international conferences and local stakeholder events.Registration detailsThe trial is registered with the Australian New Zealand Clinical Trials RegistryACTRN12621001476820 (Universal Trial Number: U1111-1268-1117).Strengths and limitations of the studyThis is the first in-human randomised double-blind placebo-controlled phase-II clinical trial examining the efficacy, safety and tolerability of L-arginine and AGE, in preventing chronic frequent episodic migraines by assessing participant-reported pain-related outcomes, and changes in photosensitivity and retinal vessels.The double-blinded nature of the study, and the placebo run-in for 2 weeks at the beginning of the study, are strengths in trial methodology.The protocol describes the oral administration of 2 nutraceutical-based interventions as possible prophylactic treatments for chronic frequent episodic migraines, with potential for direct clinical translation of outcomes.Potential limitations of the study include the fixed-dose design of each treatment arm and thatin vivoneuroimaging methods, such as magnetic resonance imaging (MRI), will not be conducted to determine putative cerebro-vasodilatory changes to coincide with the outcome measures. Dose-response studies may be indicated.