Amitriptyline. A review of its pharmacological properties and therapeutic use in chronic pain states.

Amitriptyline is a tricyclic antidepressant agent which also has analgesic properties. Whether its analgesic effects are linked to its mood-altering activity or attributable to a discrete pharmacological action (or a combination of both) is unknown. Clinical trials demonstrate that oral amitriptyline achieves at least a good or moderate response in up to two-thirds of patients with post-herpetic neuralgia and three-quarters of patients with painful diabetic neuropathy, neurogenic pain syndromes that are often unresponsive to narcotic analgesics. Amitriptyline has also demonstrated efficacy in heterogeneous groups of patients with chronic non-malignant pain. Other possible areas of use for amitriptyline are in patients with fibromyalgia or as an adjuvant for uncontrolled cancer pain, although evidence for the latter application is limited. Adverse events resulting from the antimuscarinic activity of amitriptyline (primarily dry mouth and sedation) are commonly reported, even at the low dosages used for the control of pain. Low starting doses and careful dosage titration may help to minimise these effects. Orthostatic hypotension and tachycardia, sometimes associated with tricyclic antidepressant agents, may also pose a problem in the elderly. In summary, amitriptyline has a valuable place in the treatment of chronic pain conditions that affect the elderly provided that the drug is used judiciously to minimise adverse effects. Importantly, amitriptyline remains the best studied of the antidepressant agents in post-herpetic neuralgia and diabetic neuropathy and is an important and effective treatment option in these syndromes.