Amitriptyline is an antidepressant drug, specifically a tricyclic antidepressant medication. It is one of the most widely used TCA drug. It is prescribed for treating depression. The efficacy of Amitriptyline is synonymous to the newer class of antidepressants such as SSRI or selective serotonin reuptake inhibitors. Specifically, Amitriptyline is prescribed for the following indications:
- Anxiety disorders
- Migraine prophylaxis
- Attention Deficit Hyperactivity Disorder
- Bipolar Disorder
- Anorexia nervosa or bulimia nervosa
- Post-herpetic neuralgia
- Pain relief for ankylosing spondylitis
- Prevention of biliary dyskinesia
- Nocturnal enuresis in children
- Post traumatic stress disorder (PTSD)
Other indications of Amitriptyline include:
- Cyclic vomiting syndrome
- Carpal tunnel syndrome
- Chronic cough
- Peripheral neuropathy that may be due to diabetes or Vitamin B overdose
- Laryngeal sensory neuropathy
- Painful paresthesia
- Chronic fatigue syndrome
- Multiple sclerosis
- Functional dyspepsia
The appropriate dosage of Amitriptyline for its depression indication is higher than in the management of pain. The usual dosage for pain treatment is 10 to 50 mg a day. According to studies, tricyclic antidepressants are not considered a first line of therapy for depression because of being high risk for overdose. Other antidepressant medications such as SNRIs and SSRIs are often used initially.
Amitriptyline is available in various brand names, but one of the most popular brands is Elavil. Amitriptyline overdose is related to increased ingestion of Amitriptyline by patients.
Overdose Amount of Amitriptyline
Ingestion of up to 750 mg of Amitriptyline by an adult results in Amitriptyline overdose.
Signs and Symptoms
The signs and symptoms of Amitriptyline overdose is mainly due to the anticholinergic effects of the drug at the different organs in the body as well as the brain. The heart may also suffer symptoms because of quinidine-like effects on the heart muscles. Signs and symptoms of Amitriptyline overdose include:
1. Altered metal Status
Drowsiness is a common symptom of Amitriptyline overdose. This results from the inhibition of the nerve impulse transmission in the central nervous system. Confusion may also be experienced. The presence of altered metal status may also lead to hallucinations by the patient.
This happens because of the increase in the serotonin and norepinephrine levels at the nerve terminals thereby making the nerved impulse transmission less stable.
3. Heart blocks and arrhythmias
The effects of Amitriptyline overdose in the heart results from the impediment of the cardiac conduction system thereby inhibiting the action potentials from the cardiac pacemaker.
4. Widened QRS complex in ECG tracing
The widened QRS complex results from the reduction in the sodium influx in the myocardium. Widened QRS complex is usually seen in patients having Amitriptyline overdose or toxicity.
The alpha adrenergic receptors in the blood vessel walls are also blocked by Amitriptyline overdose thereby preventing vasoconstriction and leading to profound vasodilation because of the increased level of Amitriptyline in the blood.
6. Dry skin
This effect of Amitriptyline overdose results from the anticholinergic properties of Amitriptyline overdose.
7. Dilated pupils
This also results from the blockade of the alpha adrenergic receptors leading to dilation of the pupils. Dilated pupils are usually seen in patients with severe Amitriptyline overdose
8. Urinary retention
The anti-cholinergic properties of Amitriptyline overdose lead to the prevention of the acetylcholine to go to the neuromuscular junction for muscle contraction. As a result, the bladder loses its tone leading to urinary retention.
9. Slow respiration
The slowing of the respiration may be due to the CNS depression that results in depression of the respiratory center at the brain-stem This may also result from the anticholinergic activity of Amitriptyline overdose leading to poor contraction of the respiratory muscles. The patient must be monitored for possible respiratory depression.
Hypothermia is also a possible symptom of Amitriptyline overdose because of the loss of heat through vasodilatation.
Long term effects of Amitriptyline Overdose
1. Respiratory depression
Respiratory depression is a possible long-term effect or complication of Amitriptyline overdose because of the depression of the CNS and the respiratory muscles.
Coma is the result of CNS depression that may further lead to the death of the patient suffering from Amitriptyline overdose
Causes and Risk factors
The main cause of Amitriptyline overdose is ingestion of large amounts of Amitriptyline. Overdose is mainly seen in pediatric clients as an accidental ingestion of Amitriptyline pills. Amitriptyline overdose may also be seen in depressed clients who are suicidal because TCAs commonly do not take effect immediately after initiation of the treatment. In this line, monitoring of depressed clients should be ensured in order to prevent Amitriptyline overdose.
Diagnosis of Amitriptyline Overdose
In order to identify TCA overdose diagnostic tests must be carried out; this includes an ECG. Electrocardiogram is necessary in order to monitor the cardiac functioning and identify arrhythmia, heart blocks and ECG changes such as a widened QRS complex. A blood test may also identify the actual TCA level in the blood.
Treatment of Amitriptyline Overdose
Treatment for Amitriptyline overdose include symptomatic relief as well as detoxifying the body from the high amounts of Amitriptyline in the blood. Possible treatments for Amitriptyline overdose include:
1. Administration of Activated Charcoal
Activated charcoal may be given by mouth in conscious clients and by naso-gastric tube in patients with altered metal status. Activated charcoal is given in order to absorb the Amitriptyline present in the stomach and prevent possible absorption in the intestines. A second dose of activated charcoal is sometimes necessary.
2. Sodium bicarbonate infusions
Sodium bicarbonate is given to treat possible acidosis because of Amitriptyline overdose. Patients with arrhythmias and QRS prolongation may also meed sodium bicarbonate.
3. Anticonvulsant medications
Intravenous diazepam may be given in order to control the seizures or convulsions. Phenytoin is not to be given even if it is an anticonvulsant drug because it may lead to further blocking of the sodium channels that may lead to more serious arrhythmias.
4. Oxygen therapy
Oxygen inhalation is necessary in order to prevent respiratory collapse and ease the breathing of the client.
Vasopressor drugs such as Neo-synephrine may be used in order to normalize the blood pressure.
The antidote for anticholinergic toxicity such as Amitriptyline overdose includes physostigmine. This is a cholinesterase inhibitor that increases the amount of acetylcholine in the neuromuscular junction. However, it should not be used in Amitriptyline toxicity because of possible seizures.