| Amitriptyline Pharmacology |
| Amitriptyline |
| About Amitriptyline |
| Tricyclic Antidepressant (Tertiary Amine), anticholinergic. |
| Mechanism of Action of Amitriptyline |
| Amitriptyline acts by inhibiting the re-uptake of Noradrenaline and Serotonin (5 HT) in the CNS nerve terminals .This will result in an increased concentration of neurotransmitters in the synaptic cleft and produces antidepressant effect. Amitriptyline more selectively inhibit reuptake of Serotonin than Noradrenaline. Amitriptyline also has anticholinergic activity. It is also useful in migraine prophylaxis. The monoamine uptake blocking property is related to migraine prophylactic activity. These are suited for patient with depression. |
| Pharmacokinets of Amitriptyline |
| Absorption: Amitriptyline is rapidly absorbed after oral administration. Distribution: It is widely distributed in the body in protein bound form Metabolism: Imipramine is metabolised in the liver to the active metabolite Nortriptyline. Excretion: Drug is excreted mainly through urine |
| Onset of Action for Amitriptyline |
| 2 – 6 weeks |
| Duration of Action for Amitriptyline |
| Up to 6 weeks |
| Half Life of Amitriptyline |
| 20 – 30 hours |
| Side Effects of Amitriptyline |
| 1.Drowsiness 2 Dizziness 3.Nausea 4.Vomiting 5.Blurred vision 6.Difficulty in micturition 7.Tachycardia 8.Hypotension 9.Arrhythmia 10.Dryness of mouth 11.Constipation 12.Confusion 13.Headache 14.Sedation 15.Agranulocytosis 16.Urticaria 17.Rash 18.Jaundice 19.Anorexia 20.Impotence 21.Loss of libido 22.Galactorrhea 23.Gynecomastia |
| Contra-indications of Amitriptyline |
| 1.Hypersensitivity to Amitriptyline 2.Myocardial infarction 3.CHF 4.Severe liver disease |
| Special Precautions while taking Amitriptyline |
| 1.Renal impairment 2.Hepatic impairment 3.Cardiac arrhythmia 4.Myocardial infarction 5.Tachycardia, 6.Heart failure 7.Strokes 8. Angle closure glaucoma 9.History of urine retention 10. Increased intraocular pressure 11.Hyperthyroidism, 12.Alcoholics 13.Patient at risk for suicide 14. Slowly withdraw the drug with caution 15.Patient should be cautioned against driving vehicle, operating machine and activities requiring mental alertness or judgment |
| Pregnancy Related Information |
| Use with caution. |
| Old Age Related Information |
| Use with caution. |
| Breast Feeding Related Information |
| Use with caution. |
| Children Related Information |
| Use with caution CHILDREN< 12 years: contraindicated NEONATES: contraindicated |
| Indications for Amitriptyline |
| 1.Depression, 2.Prophylaxis of migraine, 3.Bulimia nervosa, 4.Nocturnal enuresis. |
| Interactions for Amitriptyline |
| Anticholinergics : Enhanced effect of anticholinergics may occur. Barbiturates : Serum level of amitriptyline decreased; additive respiratory depressant effect. Clonidine : Hypertensive crisis. Dicoumarol : Increase in anticoagulation effects. Disulfiram : Acute organic brain syndrome. Fluoxetine & Haloperidol : Potentiate action of amitriptyline. Levodopa : Its bioavailability is reduced, hypertensive episodes. MAOIs, Furazolidone : Seizures, sweating, coma, hyperexcitabilty, hyperthermia, tachycardia, mydriasis, confusion, DIC. (Disseminated Intravascular Coagulation) and death. Oral Contraceptives and Phenothiazines : Increase plasma levels of imipramine. Smoking : Increases metabolic bio-transformation. Alcohol : Sedative effect of alcohol potentiated. |
| Typical Dosage for Amitriptyline |
| Adult: 25 mg 3 times a day dose can be gradually increased up to 150 mg / day. Maintenance dose: 50 – 100 mg / day Maximum daily dose: 300 mg Prophylaxis of migraine: 10 mg at bed time. Dose can be gradually increased up to 100 mg. Children: Nocturnal enuresis Children 12 – 16 years: 25 – 50mg to be taken 1 hour before bed time |
| Schedule of Amitriptyline |
| H |
| Storage Requirements for Amitriptyline |
| Store at room temperature in a tightly closed container. Protect from light. Keep out of the reach of children. |
| Effects of Missed Dosage of Amitriptyline |
| Take the missed dose as soon as noticed and if it is the time to take the next dose then skip the missed dose. |
| Effects of Overdose of Amitriptyline |
| Give supportive measures and treatment. Remove the drug from the body by inducing emesis and gastric lavage. Activated charcoal can be given to reduce the absorption of the drug. Seizure can be treated with Diazepam or Phenytoin, arrhythmia with Lidocaine, and acidosis with Sodium bicarbonate. |