Flupirtine in pain management: pharmacological properties and clinical use

Flupirtine is a centrally acting, non-opioid analgesic that is available in a number of European countries for the treatment of a variety of pain states. The therapeutic benefits seen with flupirtine relate to its unique pharmacological properties. Flupirtine displays indirect NDMA receptor antagonism via activation of potassium channels and is the first representative of a pharmacological class denoted the 'selective neuronal potassium channel openers'. The generation of the M-current is facilitated by flupirtine via the opening of neuronal Kv7 potassium channels. The opening of these channels inhibits exaggerated neuronal action potential generation and controls neuronal excitability. Neuronal hyperexcitability is a physiological component of many pain states such as chronic pain, migraine and neurogenic pain. Although large-scale clinical trials are lacking, the clinical trial database available to date from smaller-scale studies, together with extensive clinical experience, indicate that flupirtine effectively reduces chronic musculoskeletal pain, migraine and neuralgias, amongst other types of pain. In addition, flupirtine produces, at recommended clinical doses, muscle-relaxing effects in the presence of abnormally increased muscle tension. Its analgesic and muscle-relaxant properties were comparable to tramadol and chlormezanone, respectively, in two prospective trials in patients with lower back pain. Cytoprotective, anti-apoptotic and antioxidant properties have also been associated with flupirtine use in a small number of studies to date. When provided as combination therapy with morphine, flupirtine increases the antinociceptive activity of morphine 4-fold. Flupirtine displays superior tolerability when compared with tramadol and pentazocine. The most common adverse effects associated with flupirtine use are drowsiness, dizziness, heartburn, dry mouth, fatigue and nausea. With respect to its molecular structure, mechanism of action and adverse event profile, flupirtine is a unique drug. Flupirtine is an analgesic with many potential therapeutic benefits that may prove useful in the treatment of many disease states.