Promethazine Pharmacology

Promethazine

About Promethazine
A first-generation H1 antagonist, a phenothiazine derivative, Antihistamine,antiemetic,sedative.
Mechanism of Action of Promethazine
Antiallergic actions: Promethazine mainly acts on H1 receptor. It competes with Histamine for H1 receptor. It does not affect the release of Histamine. It blocks the Histamine actions on smooth muscles (GIT, uterus, blood vessel & bronchi) and reduces Histamine induced excess salivary secretion. It has anticholinergic actions. Promethazine produces sedation by inhibiting the stimuli to the brain stem reticular system.
Antiemetic and Antivertigo actions: The central antimuscarinic actions of antihistamines are responsible for their antivertigo and antiemetic effects. They suppress end organ receptors or inhibit central cholinergic action. It also acts on Chemoreceptor trigger zone.
Migraine: Promethazine is used in migraine due to its sedative as well as antiemetic actions.
Anaesthetic adjuncts: Promethazine is used as anaesthetic adjunct due to its sedative, antiemetic and anticholinergic properties.

Pharmacokinets of Promethazine
Absorption: It is well absorbed after oral administration. Distribution: It is distributed widely in the body. Metabolism: It is metabolised in the liver .Excretion: It is excreted mainly through urine. Small amount of drug is excreted through faeces and breast milk.
Onset of Action for Promethazine
15 - 60 minutes
Duration of Action for Promethazine
12 hours
Half Life of Promethazine
10 - 15 hours
Side Effects of Promethazine
1. Tardive dyskinesia
2. Extrapyramidal reactions
3. Drowsiness
4. Sedation
5. Dizzines
6. Hypotension
7. Dry mouth
8. Constipation
9 .Blurred vision
10. Agranulocytosis
11. Photosensitivity
12. Insomnia
13. Weight gain
14. Cholestatic jaundice
Contra-indications of Promethazine
1.Hypersensitivity to Promethazine
2.Comatose
3.Blood dyscrasias
4.Patient taking antidepressants
5.Liver damage
Special Precautions while taking Promethazine
1. Renal impairment
2. Hepatic impairment
3. Cardiovascular disease
4. Pheochromocytoma
5. Hypocalcaemia
6. Epilepsy
7. Cholestatic jaundice
8. Patient exposed to extreme heat or cold or phosphorus insecticides
9. Ceribrovascular disorder
10. Patient on ECT
11. Reaction to Insulin
12. Prostatic hyperplasia
13. Glaucoma
14. Peptic ulcer
15. Slowly withdraw the drug with caution
Pregnancy Related Information
Contraindicated
Old Age Related Information
Use with caution
Breast Feeding Related Information
Contraindicated
Children Related Information
Use with caution
CHILDREN (below 2 years): Contraindicated
NEONATES: Contraindicated
Indications for Promethazine
1. Motion sickness
2. Nausea
3. Sedation
4. Allergy
5. Migraine
6. Vertigo
7. Anticough ingredient
8. Anaesthetic adjuncts
Interactions for Promethazine
Alcohol: CNS depression, extrapyramidal reactions.
Aluminium salts: Decrease efficacy.
Antacids should be given 1 hour before or 2 hours after promethazine.
Anticholinergics: Decrease efficacy and increase the anticholinergic side-effects of promethazine.
Barbiturates: Decrease efficacy.
Barbiturate anaesthetics: Increase frequency and severity of neuromuscular excitation and hypotension.
Bromocriptine: Efficacy decreased by promethazine.
Charcoal: Prevents absorption of promethazine.
Lithium: Disorientation, unconsciousness and extrapyramidal symptoms.
Meperidine: Excessive sedation and hypotension.
TCAs: Serum concentration increased by promethazine.
Propranolol: Increased plasma levels of both drugs.
MAOIs: Additive orthostatic hypotensive effect.
Lab tests: Pregnancy tests: False positive results.
Plasma bound iodine (PBI): Increase in PBI occurs.
Typical Dosage for Promethazine
Adult:
Motion sickness: 50 mg / day in 2 divided dose
Allergy: 25 mg at bed time
Nausea: 12.5 - 25 mg / day
Sedation: 25 - 50 mg at bed time
Children:
Motion sickness: 12.5 - 25 mg / day
Allergy: 6.25 - 12. 5 mg 3 times a day
Sedation: 12.5 - 25 mg at bed time
Schedule of Promethazine
G
Storage Requirements for Promethazine
The drug should be kept at 15 - 25 degree C in a tightly closed container. Protect from heat and light. Keep out of the reach of children
Effects of Missed Dosage of Promethazine
Take the missed dose as soon s noticed and if it is the time to take the next dose then skip the missed dose.
Effects of Overdose of Promethazine
Give supportive measures and treatment. Gastric lavage has to be done. Hypotension can be treated with IV fluids, seizure with Diazepam or Barbiturates, arrhythmia with Phenytoin and excretion of drug can be increased by acidification of urine.

Home Delivery for Promethazine in Your City

Medicine India is just a publishing medium for medicine related information and does not provide services or sales of medicines including promethazine.

However, we do publish a comprehensive directory of Pharmacies, Chemists and Druggists in cities all over India. You can use this directory to find the medicine stores in your city (or area) that provide home delivery services for promethazine and other medicines and health products. Home delivery services for promethazine may be free or they may cost you depending on the pharmacy and the minimum order requirements. It would be best to get this clarified while placing the order.

Please be aware that you should take promethazine only if a doctor has recommended or prescribed it. Some or all pharmacies who provide a home delivery service for medicines might insist on a prescription for promethazine before they complete the sale. You can get this information while placing the order for promethazine with the pharmacy.

Promethazine is a generic medicine name and there are several brands available for it. Some of the brands for promethazine might be better known than promethazine itself. If the pharmacy that's willing to deliver medicines to your home doesn't have promethazine in stock, you can ask for one of the branded alternatives for promethazine.