Portal de Periódicos da CAPES

Venlafaxine for the Treatment of Neuropathic Pain

2000; Elsevier BV; Volume: 19; Issue: 6 Linguagem: Inglês

10.1016/s0885-3924(00)00151-2

1873-6513

A. Pernia, J.A. Micó, Enrique J. Calderón, L. M. Torres,

Musculoskeletal pain and rehabilitation

To the Editor: The use of antidepressants in neuropathic pain syndromes is well-established.1McQuay H.J. Tramer M. Nye B.A. Carroll D. Wiffen P.J. Moore R.A. A systematic review of antidepressants in neuropathic pain.Pain. 1996; 68: 217-227Abstract Full Text Full Text PDF PubMed Scopus (817) Google Scholar Tricyclic antidepressants have been found to be superior to selective serotonin reuptake inhibitors.2Max M.B. Lynch S.A. Muir J. Shoaf S.E. Smoller B. Dubner R. Effects of desipramine, amitriptyline, and fluoxetine on pain in diabetic neuropathy.N Engl J Med. 1992; 326: 1250-1256Crossref PubMed Scopus (1006) Google Scholar However, side effects such sedation, hypotension, and urinary retention often limit the tolerability of these medications. It would be extremely useful to identify compounds that share the ability of the tricyclics to relieve neuropathic pain but are relatively free from the drug's many toxic effects. Tricyclic antidepressants are thought to relieve pain by blocking neuronal reuptake of serotonin and norepinephrine, potentiating these transmitters' inhibitory effects in nociceptive pathways.3Valverde O. Micó J.A. Maldonado R. Mellado M. Gibert-Rahola J. Participation of opioid and monoaminergic mechanisms on the antinociceptive effect induced by tricyclic antidepressants in two behavioral pain test in mice.Prog Neuropsychopharmacol Biol Psychiatry. 1994; 18: 1073-1092Crossref PubMed Scopus (91) Google Scholar Antidepressant compounds without a tricyclic structure but with these biochemical properties, such as mirtazapine, have proven to be effective in patients with chronic pain.4Brannon G.E. Stone K.D. The use of mirtazapine in a patient with chronic pain.J Pain Symptom Manage. 1999; 18: 382-385Abstract Full Text Full Text PDF PubMed Scopus (36) Google Scholar Venlafaxine is a selective serotonin and norepinephrine reuptake inhibitor that has little anticholinergic activity and could, in theory, provide a useful alternative to tricyclic antidepressants for the treatment of neuropathic pain. We describe here a successful treatment with low doses of venlafaxine of a patient with neuropathic pain resistant to conventional analgesics. A 32-year-old woman had undergone corrective surgery for scoliosis 10 years previously. She presented with one year of mid-back pain. The patient described the pain as paroxysms of the electrical shock or discharge type; she experienced this pain several times each day, and the phenomena of hyperalgesia and allodynia were experienced in the same area. Image studies (plain radiography and computerized tomography) revealed a root compression at the level of the dorsal fifth vertebra caused by the material used in the osteosynthesis. During the year of worsening pain, a variety of treatments had been received: physiotherapy, acetaminophen, metamizol, and nonsteroidal anti-inflammatory drugs. None controlled the pain satisfactorily. The case was therefore referred to the Pain Treatment Unit. In the study conducted by the Unit, the patient reported a maximum level of pain of 80 out of 100 on the Visual Analogue Scale (VAS), in addition to the features of the pain previously described. The Hamilton scales for depression and anxiety did not provide any significant data. On presentation, treatment consisted of piroxicam 20 mg/day. The clinical condition was diagnosed as a mixed nociceptive and neuropathic etiology, secondary to radicular irritation caused by osteosynthesis material. As the primary therapeutic measure, we administered venlafaxine 37.5 mg twice daily with the piroxicam. After 7 days of treatment, the patient reported considerable symptomatic relief, with a maximum level of pain of 35 on the VAS; also the electrical discharge-type paroxysms and the phenomena of hyperalgesia and allodynia had occurred on isolated occasions during the 7 days of treatment. At 2 months, the patient continued to report satisfactory symptomatic control of the pain, without any need to modify the initial dose, with good tolerance of medication, and without the anticholinergic side effects typical of the tricyclics. Venlafaxine appears to have helped this patient's neuropathic pain independently of its antidepressive effects. In fact, the patient was free from any depression or anxiety as measured by the respective Hamilton scales. In a previous report, venlafaxine was effective in a case of low back pain associated with a severe depression.5Songer D.A. Schulte H. Venlafaxine for the treatment of chronic pain.Am J Psychiatry. 1996; 153 ([letter]): 737PubMed Google Scholar These cases are consistent with preclinical studies showing the efficacy of venlafaxine in rats with experimental mononeuropathy.6Lang E. Hord A.H. Denson D. Venlafaxine hydrochloride (Effexor) relieves thermal hyperalgesia in rats with an experimental mononeuropathy.Pain. 1996; 68: 151-155Abstract Full Text Full Text PDF PubMed Scopus (85) Google Scholar Recently, a theoretical study demonstrated the similarities between venlafaxine and tramadol,7Markowitz J.S. Patrick K.S. Venlafaxine-Tramadol similarities.Med Hypotheses. 1998; 51: 167-168Abstract Full Text PDF PubMed Scopus (64) Google Scholar an atypical analgesic that alleviates neuropathic pain.8Sindrup S.H. Andersen G. Madsen C. Smith T. Brosen K. Jensen T.S. Tramadol relieves pain and allodynia in polyneuropathy a randomised, double-blind, controlled trial.Pain. 1999; 83: 85-90Abstract Full Text Full Text PDF PubMed Scopus (324) Google Scholar Like venlafaxine, tramadol is able to inhibit the reuptake of noradrenaline and serotonin, and, in addition, tramadol activates the mu-opioid receptor.9Raffa R.B. Friderichs E. Reimann W. Shank R.P. Codd E.E. Vaught J.L. Opioid and non opioid components independently contribute to the mechanism of action of tramadol, an 'atypical' opioid analgesic.J Pharmacol Exp Ther. 1992; 260: 275-285PubMed Google Scholar In this context, it has been demonstrated that tramadol elicits antidepressant-like properties.10Rojas-Corrales M.O. Gibert-Rahola J. Micó J.A. Tramadol induces antidepressant-type effects in mice.Life Sci. 1998; 63: PL175-PL180Crossref PubMed Scopus (89) Google Scholar Interestingly, the analgesic effect of venlafaxine in animals is blocked by naloxone, a mu-opioid antagonist.11Schreiber S. Backer M.M. Pick C.G. The antinociceptive effect of venlafaxine in mice is mediated through opioid and adrenergic mechanisms.Neurosci Lett. 1999; 273: 85-88Crossref PubMed Scopus (118) Google Scholar Therefore, venlafaxine could be an alternative to classical tricyclic antidepressants for use in neuropathic pain, whether or not mood disorders are present. Its mechanisms of action in the alleviation of pain may be related to the monoaminergic and opioidergic systems.