It is TGA-labelled for migraine prophylaxis, as it is also is in cases of neuropathic pain disorders,fibromyalgia and nocturnal enuresis. Amitriptyline is a popular off-label treatment for irritable bowel syndrome. Although it is most frequently reserved for severe cases of abdominal pain in patients with IBS due to the fact that it needs to be taken regularly to work and has a generally poor tolerability profile, although a firm evidence base supports its efficacy in this indication. Amitriptyline can also be used as an anticholinergic drug in the treatment of early stage Parkinson disease if depression also needs to be treated.
Eating disorders Although the few randomised controlled trials investigating its efficacy in eating disorders have been discouraging.
The symptoms and the treatment of an overdose are largely the same as for the other TCAs, including the presentation of serotonin syndrome and adverse cardiac effects. The British National Formulary notes that amitriptyline can be particularly dangerous in overdose, thus it and other tricyclic antidepressants are no longer recommended as first line therapy for depression. Alternative agents, SSRIs and SNRIs are safer in overdose, though they are no more efficacious than TCAs. English folk singer, Nick Drake, died from an overdose of Tryptizol in 1974.
The possible symptoms of amitriptyline overdose include:
The treatment of overdose is mostly supportive as there is no specific antidote for amitriptyline overdose. Activated charcoal may reduce absorption if given within 1-2 hours of ingestion. If the affected person is unconscious or have an impaired gag reflex a nasograstic tube may be used to deliver the activated charcoal in the stomach. ECG monitoring for cardiac conduction abnormalities is essential and if one is found close monitoring of cardiac function is advised. Body temperature should be regulated with measures such as heating blankets if necessary. Likewise cardiac arrhythmias can be treated with propanolol and should heart failure occur digitalis may be used. Cardiac monitoring is advised for at least five days after the overdose. Other measures include the use of inhalation anaesthetics or diazepam for convulsions and barbiturates should be avoided if possible due to the potential for additive CNS depression (that is, on top of the CNS depression caused by the amitriptyline).Dialysis is of no use due to the high degree of protein binding with amitriptyline.
Amitriptyline is readily absorbed from the gastrointestinal tract and is extensively metabolised on first-pass through the liver. It is metabolised mostly via CYP2D6, CYP3A4, CYP2C9-mediated N-demethylation into nortriptyline, which is another tricyclic antidepressant in its own right. It is 96% bound to plasma proteins, nortriptyline is 93-95% bound to plasma proteins.It is mostly excreted in the urine (around 30-50%) as metabolites either free or as glucuronide and sulfate conjugates.Small amounts are also excreted in faeces.
Brand names include (just including those used in English-speaking countries with † to indicate discontinued brands):
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