| Indication | For management of symptoms related to hay fever and other types of allergy and used to help bring up phlegm, thin secretions, and make a cough productive. |
| Pharmacodynamics | Bromodiphenhydramine is an antihistamine of the ethanolamine class. Ethanolamine antihistamines have significant antimuscarinic activity and produce marked sedation in most patients. In addition to the usual allergic symptoms, the drug also treats irritant cough and nausea, vomiting, and vertigo associated with motion sickness. It also is used commonly to treat drug-induced extrapyramidal symptoms as well as to treat mild cases of Parkinson's disease. Rather than preventing the release of histamine, as do cromolyn and nedocromil, Bromodiphenhydramine competes with free histamine for binding at HA-receptor sites. Bromodiphenhydramine competitively antagonizes the effects of histamine on HA-receptors in the GI tract, uterus, large blood vessels, and bronchial muscle. Ethanolamine derivatives have greater anticholinergic activity than do other antihistamines, which probably accounts for the antidyskinetic action of Bromodiphenhydramine. This anticholinergic action appears to be due to a central antimuscarinic effect, which also may be responsible for its antiemetic effects, although the exact mechanism is unknown. |
| Mechanism of action | Bromodiphenhydramine competes with free histamine for binding at HA-receptor sites. This antagonizes the effects of histamine on HA-receptors, leading to a reduction of the negative symptoms brought on by histamine HA-receptor binding. |
| Absorption | Well absorbed in the digestive tract. |
| Volume of distribution | Not Available |
| Protein binding | 96% |
| Metabolism | Hepatic (cytochrome P-450 system); some renal. |
| Route of elimination | Not Available |
| Half life | 1 to 4 hours |
| Clearance | Not Available |
| Toxicity | Signs of overdose include wheezing, tightness in the chest, fever, itching, bad cough, blue skin color, fits, swelling of face, lips, tongue, or throat. |