6533b832fe1ef96bd129a368

RESEARCH PRODUCT

Dose escalating safety study of CNS 5161 HCl, a new neuronal glutamate receptor antagonist (NMDA) for the treatment of neuropathic pain

subject

description

What is already known about this subject • Despite encouraging effects of N-methyl-D-aspartate (NMDA) receptor antagonists in reducing neuropathic pain of different aetiologies, the clinical use of these agents has been limited by their mainly psychotropic side-effects. • In a recent study in healthy volunteers, CNS 5161, a novel noncompetetive NMDA receptor antagonist, was well tolerated up to a dosage of 2000 µg without psychotropic side-effects. • This is the first study to evaluate the maximal tolerated dosage of CNS 5161 and to gain experience about the analgesic effect of CNS 5161 in patients with different pain syndromes. What this study adds • In patients with neuropathic pain CNS 5161 is well tolerated up to a dosage of 500 µg with the most common side-effect of increasing blood pressure, mild visual disturbances and headaches. • While no therapeutic effect can be observed in a dosage up to 250 µg, treatment with 500 µg CNS 5161 provides some indications of analgesic activity. • It appears that this effect occurs predominantly in patients with diabetic neuropathy. Aims The purpose of the current study was to establish the safety and maximal tolerated dose of CNS 5161 HCl. Methods Forty patients with chronic neuropathic pain (23 male, 17 female) were treated with escalating dosages of CNS 5161. All adverse events to study drug, blood pressure, heart rate, ECG, drug level and clinical laboratory values were monitored. Actual pain was measured on a 100-mm visual analogue scale (VAS) and ordinal verbal pain scores. Results The most commonly occurring nervous system disorder was headache, which was found more often during placebo than during CNS 5161 HCl treatment. Visual disturbances were experienced by 16.7% of patients receiving 250 µg and by 33.3% receiving 500 µg CNS 5161 HCl, but not during placebo treatment. An increase in blood pressure was observed in 8.3% of patients receiving 250 µg and in 50% of patients receiving 500 µg CNS 5161 HCl, compared with 15.4% during placebo treatment. The study was abandoned after two patients entered the 750 µg cohort due to a sustained systolic blood pressure response. Although this study was underpowered for the confirmation of efficacy, some indications of greater pain relief after 500 µg CNS 5161 compared with placebo could be observed (change in VAS between baseline and 12 h 10 ± 22 mm vs. 2 ± 19 mm; P = 0.11). Conclusions CNS 5161 HCl was reasonably well tolerated up to 500 µg. The most common adverse events were hypertension, headache and mild visual disorders.