Published: 2016-12-30

A comparative study of efficacy of gabapentin in inflammation induced neuropathic animal pain models with conventional analgesic diclofenac

Arunim Swarup, Ruchika Agarwal, Sunil Malhotra, Abhay Shankar Dube


Background: Some antiepileptic drugs have been shown to be clinically efficacious in treatment of neuropathic pain and are being used by clinicians. This study is proposed to evaluate the efficacy of these drugs as compared to conventional analgesics.

Methods: Formalin  test  has  been  used  as  the  model  of  acute and chronic  inflammatory  pain.  Formalin  has  been  characterized  by  the  occurrence  of  two  characteristic  phases  of  increased  pain  sensitivity  in  rats. The  test  drugs  have  been  administered  orally  and  scored  according  to  a  pain  scale.  Pain  has  been  quantified  by  counting  the  incidence  of  spontaneous  flinches,  shakes  and  jerks  of  the  formalin  injected  paw.  Analgesic  response  or  protection  has been  indicated  if  both  paws  are  resting  on  floor  with  no  obvious  favouring  of  injected  paw. Treatment  group  was  compared  with  appropriate  control  groups  using “student  t  test”.

Results: Per oral administration of  gabapentin  produced  no  any  marked  effect  on  early phase  response  of  formalin  test  but  significantly  suppressed  the  late  phase  response  while  diclofenac  produced  significant  antinociceptive  effect  in  both  phases  of  formalin  test.

Conclusions: Thus  we  have  observed  that  gabapentin   produced  antinociception  in  second  phase  of  formalin  test  which  reflects  chronic  inflammatory  pain.


Gabapentin, Diclofenac, Nociception, Formalin test

Full Text:



Merskey H, Albe-Fessard DG, Bonica JJ, Carmon A, Dubner R, Kerr FWL, et al. Pain terms a list with definitions and notes on usage. Pain. 1979;6:249-52.

Pain Free: Modern Drugs and Neuropathic Pain. J Korean Med Science. 2002;22:360-7.

Maizes M, Mccarberg B. Antidepressant and antiepileptic drugs for chronic noncancer pain. Am Fam Physician. 2005;71:483-90.

Assi D, Azim A, Rahman A, Mahran S. Analgesic effects of tramadol-diclofenac combination and their interaction with sycostimulant drugs in mice and rats. Eur J Pharmacol. 1996;312:132-8.

Carrie K, Jones SC. Efficacy of duloxitine, a potent and balanced serotonergic and noradrenergic reuptake inhibitor, in inflammatory and acute pain models in rodents. J Pharmacol Exp Ther. 2005;313:726-32.

Vogel HG, Vogel WGH, editors, Drug discovery and evaluation-pharmacological assays. 2nd ed. New York: Verlog Springer publication; 1996.

Sukriti, Hota D, Pandhi P. Potentiation of antihyperalgesic activity of diclofenac by nimodipine in a formalin model of facial pain in rats. Exp Clin Pharmacol. 2004;26:253-6.

Hernandez GC, Soto VG, Ortiz MI. Pinacidil increases diclofenac antinociception in the formalin test. Proc West Pharmacol Soc. 2005;48:55-8.

Yoon MH, Choi J, Kwak SH. Characteristic of interaction between intratheca gabapentin and either clonidine or neostigmine in the formalin test. Anesth Analg. 2004;98:1374-9.

Carlton SM, Zhou S. Attenuation of formalin induced nociceptive behaviors following local peripheral injection of gabapentin. Pain. 1998;76:201-7.

Heughan CE, Sawynok J. The interaction between gabapentin and amitryptyline in the rat formalin test after systemic administration. Anesth Analg. 2002;94:975-80.

Field MJ, Oles RJ, Lewis AS, McCleary S, Hughes J, Singh L. Gabapentin (neurontin) and s-(+)-3-isobutylgaba represent a novel class of selective antihyperalgesic agents. Br J Pharmacol. 1997;121:1513-22.

Urban MO, Ren K, Park KT, Campbell B, Anker N, Stearns B, et al. Comparison of the antinociceptive profiles of gabapentin and 3 methyl gabapentin in rat models of acute and persistent pain: Implications for mechanism of action. J Pharmacol Exp Ther. 2005;313:1209-16.

Dickenson D, Sullivan AF. Peripheral origins and central modulation of subcutaneous formalin induced activity of rat dorsal horn neurons. Neurosci Lett. 1987;83:207-11.

Field MJ, Hughes J, Singh L. Further evidence for the role of the alpha2 delta subunit of voltage dependent calcium channels in models of neuropathic pain. Br J Pharmacol. 2000;13:282-6.

Cheng JK, Lai YJ, Chen CC, Cheng CR, Chiou LC. Magnesium chloride and ruthenium red attenuate the antiallodynic effect of intrathecal gabapentin in arat model of postoperative pain. Anesthesiology. 2003;98:1472-9.