Comparison of Oxcarbazepine Versus Carbamazepine in the Management of Trigeminal Neuralgia in Patients Presenting in Outpatient Department of Neurology in Jinnah Postgraduate Medical Centre

INTRODUCTION:

According to the International Headache Society, Trigeminal neuralgia is defined as "a disorder characterized by recurrent unilateral brief electric shock-like pain, abrupt in onset and termination, limited to the distribution of one or more divisions of the trigeminal nerve and triggered by innocuous stimuli" [1]. The trigeminal nerve (V) is the fifth and largest of all cranial nerves, and it is responsible for detecting sensory stimuli that arise from the craniofacial area including the forehead, cheek, and lower jaw [2]. It is a highly debilitating disorder that impacts on basic human functions such as talking, eating, drinking and touching the face, thereby resulting in a poor quality of life [3, 4].

Trigeminal neuralgia is considered a rare condition, affecting 4 to 13 people per 100,000 people annually. Women are more commonly affected than men. The female-to-male prevalence ratio ranges from 1.5 to 1.7 to 1. Most cases of trigeminal neuralgia occur after age 50, but the disease may be seen in the second and third decades of life; trigeminal neuralgia is rarely diagnosed in childhood. The lifetime prevalence of trigeminal neuralgia in population-based studies is estimated at 0.16% to 0.3% [5, 6]. A Pakistani study by Usman J, et al. audited the trigeminal neuralgia patients visiting the tertiary care hospital over a period of two years and reported a 0.46% prevalence of trigeminal neuralgia [7].

Trigeminal neuralgia is usually suspected through historical, physical and clinical examination findings. These patients should undergo neuroimaging with magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) whenever possible for confirmation of trigeminal neuralgia [6, 8, 9]. Medical therapy is the preferred initial therapeutic intervention for patients with trigeminal neuralgia. The antiepileptics carbamazepine or oxcarbazepine are the preferred initial therapeutic agents [10]. Carbamazepine is FDA indicated for epilepsy, trigeminal neuralgia, and acute manic and mixed episodes in bipolar I disorder [11]. Oxcarbazepine is an analogue of carbamazepine and is often used in acute orofacial pain episodes lasting seconds, as well as in the trigeminal nerve and its branches. Oxcarbazepine is preferred over carbamazepine because it has advantages over carbamazepine and lesser negative effects [12]. A study by Iqbal S, et al was conducted on efficacy of carbamazepine and oxcarbazepine for treating trigeminal neuralgia and reported a complete response in 42.9% of patients with carbamazepine and 67.9% of patients with oxcarbazepine. Frequency of adverse effects was higher for carbamazepine as that of Oxcarbazepine. i.e. 35.7% vs. 14.3% [13]. Another study by Di Stefano G, et al. reported that the initial proportion of responders was 88.3% with carbamazepine, and 90.9% with oxcarbazepine. Side effects occurred more frequently in patients treated with carbamazepine (43.6%) than with oxcarbazepine (30.3%) [14].

The rationale of the study is to compare the efficacy of oxcarbazepine and carbamazepine in the management of trigeminal neuralgia in patients presenting in the outpatient department of neurology at Jinnah Postgraduate Medical Centre. International and local data is very scarce regarding the comparisons of both of these drugs for treating trigeminal neuralgia. However, the effects of these drugs have been documented in the literature in comparison to other drugs or as a triple therapy combination. So, taking both drugs as monotherapy for treating trigeminal neuralgia can lead us to conclude which drug is superior as a monotherapy so that, in the future, drug with better efficacy will be preferred. The results of the study will be helpful in the selection of an appropriate and more effective drug for the treatment of trigeminal neuralgia.