Comparative Study Between Valproate and Memantine in the Prophylactic Management of Episodic Migraine.

Migraine is a primary headache, currently one of the three most disabling diseases globally. It has an annual and lifetime prevalence of 18% and 33% in women, and 6 to 13% in men, respectively, with a predominance in women (3: 1). The age of onset with the highest prevalence is between 25 and 55 years.

Migraine is described by the International Headache Society (IHS) as recurrent episodes of headache lasting 4 to 72 hours, characterized by unilateral location, pulsatile character, moderate or severe intensity, worsening with physical activity, and association with nausea or photophobia and phonophobia. The IHS also classifies migraine based on the frequency of attacks: episodic migraine when the headache occurs on less than 15 days a month, and chronic migraine, when the headache occurs 15 or more days a month for three months and at least eight days a month with characteristics of migraine headache.

The subtypes of migraine concerning their clinical presentation are migraine with aura and without aura.4 Up to one-third of patients present migraine aura, with visual symptoms being the most frequent.

Four phases have been identified during a migraine: prodromal phase, aura, headache, and postdrome. The prodromal phase is characterized by premonitory symptoms hours before the headache, including difficulty concentrating, irritability, fatigue, repetitive yawning, stiff neck, and photophobia.

Recurrent episodes characterize the aura, lasting from 5min to 60min, with transient unilateral visual, sensory, or other CNS symptoms that develop progressively, usually precede headache and symptoms associated with migraine.4 The aura's genesis is activated by the NMDA (N-methyl-D-aspartate) receptor and disseminated cortical depression. Disseminated cortical depression is an extreme depolarization of the cell membranes of the glia and neurons that produce an alteration of the ionic gradient, an increase in extracellular potassium concentrations, glutamate release, and a transient increase followed by a decrease in cerebral blood flow.

The pain phase in migraine is due to the activation and sensitization of the trigeminovascular pain pathway, which innervates intracranial structures, including the eye, the dura mater, large braincases, and the venous sinuses. It has been shown to involve neuronal presynaptic activation by ID serotonin receptors (5-HT 1D), resulting in the release of the calcitonin gene (CGRP) and pituitary adenylate cyclase-activating polypeptide (PACAP-38), which are neuroinflammatory peptides. The post-synaptic effect on the meninges includes the activation of the arachidonic acid cascade, which conditions inflammation and vasodilation, stimulates the nociceptive afference of pain first branch of the trigeminal nerve.

The diagnosis of migraine is clinical and must meet the criteria of the IHS International Classification of Headaches (ICH-3), which are for migraine without aura:

At least five crises that meet criteria B-D. A. Headache episodes are lasting 4 to 72 hours (untreated or unsuccessfully treated).

1. The headache has at least two of the following four characteristics:
2. Unilateral location.
3. Pulsatile character.
4. Pain of moderate or severe intensity.
5. Made worse by or conditions the abandonment of habitual physical activity (e.g., walking or climbing stairs).
6. At least one of the following during the headache:
7. Nausea and vomiting.
8. Photophobia and phonophobia. D. No better explanation by another diagnosis of ICHD-III.

The non-pharmacological treatment of migraine goes hand in hand with the pharmacological one; one is to avoid the triggers of the migraine attacks and carry out the lifestyle modifications. Pharmacological treatment is divided into acute (administered at the time of headache) and prophylactic (administered daily to reduce the chances of migraine episodes).

The objective of prophylactic treatment is to reduce the frequency, duration, and severity of migraine attacks, improve the response to acute treatment, improve functionality, and reduce disability.

The American Academy of Neurology recommends initiating prophylactic treatment in patients with migraine with one or more of the following characteristics9

1. Recurrent migraine, which interferes with the patient's daily life and quality of life.
2. Frequent headaches.
3. That they have an inadequate response or contraindication to abortive treatment.
4. Adverse events to abortion treatment.
5. Uncommon migraine conditions: ophthalmoplegic migraine, basilar migraine, hemiplegic, prolonged aura, migraine infarction.

The IHS defines the response to treatment as a decrease equal to or greater than 50% in the frequency of migraine attacks compared to the baseline situation.

The American Academy of Neurology guideline for the prophylactic drug treatment of episodic migraine classifies divalproex sodium, valproate sodium (VPA), topiramate, metoprolol propranolol as level A (Drugs with established efficacy ).

Valproic acid (2-propylpentaenoic acid) was first synthesized in 1882 as an analog of valeric acid, naturally found in valerian. Anyone of Valproic acid, sodium valproate, or a mixture of the two (sodium valproate) has a mechanism of action characterized by increasing or improving GABA neurotransmission, blocking voltage-gated sodium channels, and T-type calcium channels. In 2013, Cochrane conducted the review: Valproate for the prophylaxis of episodic migraine (Linda et al.), where they evaluated ten clinical trials. Two crossover clinical trials for sodium valproate demonstrated a significant reduction in headache frequency than placebo (MD -4.31 95% CI -8.32 to -0.30), which shows us in clinical terms an approximate reduction of four headaches for every 28 days. Jensen 199413 showed that sodium valproate is superior to placebo (OR 4.67; 95% CI 1.54 - 14.14), suggesting that patients are three times more likely to present a reduction equal to or greater than 50% in the frequency of headaches compared to placebo. The recommended dose for migraine headaches is 500-1000mg per day. The most common adverse effects are asthenia, fatigue, dizziness/vertigo, nausea, tremor, and weight gain.

In recent years, interest has increased in glutamate receptor antagonists for migraine prophylaxis, such as memantine. Within the pathophysiology of migraine, glutamate is implicated in disseminated cortical depression, trigeminal-vascular activation. Other studies corroborate its role by reporting elevated glutamate levels in the cerebrospinal fluid in patients with chronic migraine in the ictal period and elevated serum levels in migraine patients. Besides, after experimental stimulation in the dura and the ventral-posteromedial thalamic nucleus structures, elevated levels of glutamate in the trigeminal-cervical complex have been evidenced. fifteen

In 2008 Bigal and colleagues conducted the first open clinical trial, a pilot study to evaluate memantine's efficacy and safety as a prophylactic treatment in patients diagnosed with refractory migraine. A sample of 28 participants who had a baseline frequency of headache days of 21.8 days per month received memantine from 10mg to 20mg per day for three months. A decrease in the frequency of headache days was obtained to 16.1 (P <0.01). Therefore, the authors concluded that memantine as a prophylactic treatment is safe and effective in refractory migraines. In 2015, Noruzzadeh and colleagues conducted the first randomized, double-blind, placebo-controlled clinical trial to evaluate memantine's efficacy as a prophylactic treatment of migraine without aura With a sample of 52 participants, 25 with memantine (10 mg/day) and 27 with placebo. The memantine group had a more significant reduction in the frequency of migraine attacks compared to placebo, which was a difference of 2.3 attacks per month with a P <0.001.14