Amitriptyline is now considered the “Gold Standard” for treating neuropathic (nerve) pain as it has been shown to be one of the most effective and best-known drugs for this condition. It can also be used to treat chronic pain caused by arthritis, spinal problems, fibromyalgia and chronic headaches (tension headaches).
Amitriptyline was developed for use in treating depression and anxiety and belongs to a group of drugs called tricyclic antidepressants. However, it is much more common now for amitriptyline to be prescribed at lower doses to help block the chronic (long-term) pain of some conditions.
The main aim of amitriptyline used in this way is to relieve pain, relax muscles and improve pain related insomnia. At the same time, however, it may also help reduce any anxiety or depression resulting from the pain.
Amitriptyline works by changing the way the nerves send messages to the brain. When nerves are damaged or become irritated they are unable to transmit correct messages to the brain.
Chronic or persistent pain is associated with changes in the central nervous system (CNS - the spinal cord and brain) that lead to failure of adequate pain regulation. This is called pain wind-up or pain amplification and it adds to the distress caused by pain. Amitriptyline works by rebalancing certain chemicals called neurotransmitters in the CNS thus helping to reduce and stabilise the number of faulty messages that the nerves are sending to the brain. This in turn results in reduced pain sensations. These scrambled/altered messages to the brain can also affect sleep and mood, which is why amitriptyline will also help improve sleep patterns.
For persistent pain amitriptyline is started at a low dose (10 or 25 mg a day) and gradually increased in 10 or 25 mg increments each week up to a maximum of 75 mg per day as long as there aren’t any troublesome side effects. In some cases the dose might even be raised as high as 100 to 150 mg per day if necessary for the desired effect but this should only be done under the supervision of a specialist doctor.
As amitriptyline can cause drowsiness it is best taken in the evening just before going to bed.
Pain relief can begin as soon as two weeks after starting, but often it requires amitriptyline to be taken for six to eight weeks at the best dose level before one can say the drug has been given a fair trial. Some people may be tempted to stop taking the medicine because they experience side effects early on but do not feel any better. However, if they can persevere, most of the side effects will go away after a few days and then the benefits of amitriptyline can be seen.
It is not a good idea to suddenly stop taking amitriptyline, as this can cause withdrawal symptoms such as nausea, vomiting, loss of appetite, headache, giddiness, chills, insomnia, restlessness or anxiety. Withdrawal symptoms are temporary and are not due to addiction or dependence on the medicine. They can usually be avoided by stopping the medicine gradually, usually over a period of weeks or months, depending on your individual situation. Follow the instructions given by the doctor when it is time to stop treatment with amitriptyline.
People taking amitriptyline may experience a “hangover” effect, such as drowsiness, dizziness or blurred vision. These may be a problem in the short-term but should settle down within a week or so. If affected, do not drive or operate machinery.
Other common side effects are:
- Dry mouth.
- Difficulty in passing urine.
- Weight gain.
- Enhanced effects of alcohol.
Occasionally, other side-effects are reported. Please see the information leaflet in your tablet box for further details.
If you are taking a low dose, you may have no side-effects at all. If you do have side-effects, you may reduce your dose then gradually increase it again over time.
Rare side effects of amitriptyline include:
- Fast Pulse Rate.
- Sensitivity to sunlight.
- Reduced interest in sex or impotence.
- Involuntary muscle movements such as tremors or twitching.
- Low blood pressure.
- Abnormal heart beats.
Neuropathic pain and migraine prophylaxis are unlicensed indications for amitriptyline. This means that the manufacturers do not recommend its use in these conditions but there is enough evidence for a doctor to believe that it will be both effective and safe. The doctor takes personal responsibility for the prescription.
Amitriptyline should be used with caution in:
- Young adults.
- Elderly people.
- People with decreased liver function.
- Heart disease.
- People with an overactive thyroid gland (hyperthyroidism).
- People taking thyroid medication for an underactive thyroid gland (hypothyroidism).
- People with a tumour of the adrenal gland (phaeochromocytoma).
- Men with an enlarged prostate gland (prostatic hypertrophy).
- People with a history of difficulty passing urine (urinary retention).
- People with chronic constipation.
- People with a history of raised pressure in the eye or glaucoma.
- People with a history of epilepsy.
- People at risk of seizures (fits), e.g. due to alcohol/drug withdrawal, brain damage, other medicines.
- Psychotic illness, eg schizophrenia.
- Bipolar affective disorder (manic depression).
- People receiving electroconvulsive therapy (ECT).
- People with a history of suicidal behaviour or thoughts.
Amitriptyline must not to be used in:
- Cases of severe liver disease.
- People who have recently had a heart attack.
- People with a defect in the heart's electrical message pathways resulting in decreased function of the heart (heart block).
- Irregular heartbeats (arrhythmias).
- Closed angle glaucoma.
- People in a manic phase of bipolar disorder (manic depression).
- People who have taken a monoamine oxidase inhibitor antidepressant (MAOI) in the last two weeks.
- Hereditary blood disorders called porphyrias.
The patient information leaflet (PIL) is a leaflet containing specific information about medical conditions, doses and side effects. You can download a copy of the PIL here:
Patient Info Leaflet