Active substances: Gabapentin
Long term studies on the safety of these cannabinoids are yet to come.
Further, adjuvant effects of 10 and 20 mg doses of dronabinol were also observed in patients with chronic pain who are under opioid therapy 86. Although no difference in pain suppression was observed between amitriptyline and nabilone, nabilone was better in improving the quality of sleep and is considered as an alternative to amitriptyline, but its long term safety profile should be assessed further 87.
Meanwhile, the results of a clinical trial on the efficiency of fatty acid amide hydrolase FAAH inhibitor, PF-, was unsuccessful in controlling osteoarthritic pain in spite of being effective in animal models of neuropathic pain 88.
Recent trial of dextromethorphan in combination with quinidine had promising results in patients with PDN 92.
Therefore, studies consisting of agents that would reduce increased NMDA receptor activity without affecting their physiological function are yet to come. Alpha 2-Adrenoceptor Agonists Applying 0. Furthermore, clonidine along with opioid is more effective than clonidine alone to relieve pain in patients with NP 99.
Clinical studies supported its use to manage spasticity associated with multiple sclerosis MS, acquired brain injury or spinal cord injury.
Tizanidine is well tolerated, compared to clonidine, regarding the incidence of side effects, such as hypotension, bradycardia and sedation at antihyperalgesic doses, which are lower than that of clonidine.
It is used mainly in adjunction to local anesthetics owing to its ability to reduce onset, increased duration of sensory block, prolonged postoperative analgesia and reduction in the analgesic dose needed 101.
Topical Capsaicin The efficacy of capsaicin cream 0. It is an agonist of the transient receptor potential vanilloid-1 TRPV 1 causing depolarization, action potential generation and transmission of pain signals.
But on repeated application, axons expressing these receptors are desensitized thereby inhibiting pain transmission.
Although depletion of substance-P is proposed as a mechanism of action of capsaicin in pain relief, it is suggested that defunctionalisation of nociceptors fibers is the key step involved.
In a Cochrane review performed by Derry et al. Botulinum Toxin This is a neurotoxin with a protective role in spasticity, focal dystonia and chronic migraine pain. It has FDA approval for strabismus, focal dystonia, blepharospasm and upper limb spasticity indications.
Mechanism of action proposed for its therapeutic effect is not clear but inhibition of release of neural substances and neurotransmitters thereby causing reduction of neurogenic inflammation is reported 103.
Clinical trials on traumatic and diabetic neuropathic pain showed promising results with subcutaneous injections and importantly no systemic side effects were reported.
Studies involving trigeminal neuralgia, spinal cord injury, complex regional pain syndrome and PHN also showed promising results with botulinum toxin treatment with minimal side effect profile and is well tolerated 108.
Gabapentin in combination with oxycodone also showed better pain relief than these drugs alone, but had sleep disturbances as a side effect 111. Ketamine infusion in low doses along with oral gabapentin reduced the pain scores in patients with spinal cord injury and is well tolerated 112.
However, delusions were reported with this combination. Eisenberg et al. Delayed sensory blockade with no significant postoperative analgesic effects were obtained for the combination of magnesium with bupivacaine for spinal anesthesia in females undergoing cesarean section 113.
Possible Future Therapies Selective knock down of sensory neuron specific PN 3 but not NaN sodium channel gene expression with antisense oligo-deoxynucleotides in DRG neurons prevented the hyperalgesia and allodynia following nerve injury in rats 114.Peripheral neuropathies arise from disorders associated causes of neuropathy in cancer patients, as well as effective therapies-and even.