Diphenhydramine Pharmacology


About Diphenhydramine
First Generation H1 Antagonist ,Ethanolamine derivative, Antihistamine, antiemetic, antivertigo,sedative, and hypnotic.
Mechanism of Action of Diphenhydramine
Antiallergic action: It produces its antihistamine action by competitively blocking H1 receptors. It binds to the H1 receptors present in the smooth muscles of the gastrointestinal tract, bronchi, large blood vessels and uterus and inhibit Histamine induced allergic symptoms. They do not inhibit the release of Histamine.
Antivertigo and antiemetic actions: Central antimuscarinic actions of antihistamines are responsible for these effects of Diphenhydramine.
Parkinsonism: Acetyl choline receptor antagonists are used for the treatment of Parkinsonism. Diphenhydramine reduces the unbalanced cholinergic activity in striatum of parkinsonian patients.
Antitussive action: Diphenhydramine suppresses the cough reflex by a direct effect on the cough centre.
Migraine: Diphenhydramine is used in migraine due to its sedative as well as antiemetic actions.
Pharmacokinets of Diphenhydramine
Absorption: It is well absorbed after oral administration. Distribution: Diphenhydramine is widely distributed in the body including CNS in protein bound form. Metabolism: It is extensively metabolised in the liver. Excretion: Excreted primarily in urine
Onset of Action for Diphenhydramine
15 minutes
Duration of Action for Diphenhydramine
6 - 8 hours
Half Life of Diphenhydramine
2.5 - 9 hours
Side Effects of Diphenhydramine
2.Dry mouth
12.Abdominal pain
13.Urine retention
14.Thickening of bronchial secretions.
Contra-indications of Diphenhydramine
1.Hypersensitivity to Diphenhydramine
Special Precautions while taking Diphenhydramine
4.Angle closure glaucoma
5.Prostatic hyperplasia
6.Urinary tract obstruction
7.Use with caution while operating machine, driving vehicle or activities requiring mental alertness
Pregnancy Related Information
Use with caution.
Old Age Related Information
Use with caution.
Breast Feeding Related Information
Children Related Information
Use with caution
NEONATES: contraindicated
Indications for Diphenhydramine
1.Parkinson`s disease
2.Motion sickness
4.Allergy disorders
6.Productive cough
Interactions for Diphenhydramine
Incompatibility reported with amphotericin, cephalothine sodium, hydrocortisone, sodium succinate, some soluble barbiturates, some contrast media.
Typical Dosage for Diphenhydramine
Adult: 25 - 50 mg 3 - 4 times daily. Dosage should be individualised according to the needs and the response of the patient
Nonproductive cough: 100 mg / day in 4-6 times daily.
Insomnia: 50 mg at bed time
Children above 12 years: 25 - 50 mg 3 - 4 times daily. Dosage should be individualised according to the needs and the response of the patient
Nonproductive cough: 100 mg / day in 4-6 divided dose
Insomnia: 50 mg at bed time
Children age 2 -12 years: 12.5 - 25 mg 3 - 4 times daily. Dosage should be individualised according to the needs and the response of the patient.
Maximum dose: 300mg / day
Nonproductive cough: 6.25 - 12.5 mg in 4-6 times daily. Dosage should be individualised according to the needs and the response of the patient
Schedule of Diphenhydramine
Storage Requirements for Diphenhydramine
Store at 15 - 30 degree C. Protect from heat, light and moisture. Keep out of the reach of children.
Effects of Missed Dosage of Diphenhydramine
Take the missed dose as soon as noticed and if it is the time for next dose then skip the missed dose. Continue the regular schedule. Do not double the dose.
Effects of Overdose of Diphenhydramine
Give supportive measures and symptomatic treatment. Drug can be removed from the body by gastric lavage or by inducing emesis. Absorption of the drug can be reduced by administration of activated charcoal. Hypotension can be counteracted by administration of vasopressors and seizure with Phenytoin or Diazepam.

Home Delivery for Diphenhydramine in Your City

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

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 diphenhydramine and other medicines and health products. Home delivery services for diphenhydramine 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 diphenhydramine 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 diphenhydramine before they complete the sale. You can get this information while placing the order for diphenhydramine with the pharmacy.

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