First Gen. Antihistamine Drugs
- Diphenhydramine (Benadryl)
- Chlorpheniramine (Chlor-Trimeton)
- Brompheniramine (Lodrane, LoHist,Bidhist)
- Hydroxyzine (Vistaril)
- Promethazine (Phenergan)
- Clemastine (Tavist)
- Triprolidine (Zymine)
- Third line therapy for allergic rhinitis
- Not as effective as INGC
- Three categories of effect;
- May shift balance from H1 receptor form to the inactive H1 receptor form thereby down regulating the H1 receptor activity
- Blocks increased vascular permeability, pruritis, bronchial smooth muscle constriction, and can cause mucosal drying
- May also effect eosinophil survival
- May cause CNS depression, use caution with driving.
- Anticholinergic effects. Dry mouth, urinary retention, possible worsening of narrow angle glaucoma, confusion.
- Acetylcholinesterase inhibitors decrease effect.
- Anticholinergics increase side effects.
- Additive effect with central nervous system depressants.
- May increase the arrhythmogenic effect of phenothiazines.
- Acute asthma
- FDA has now issued a warning that use of these medications in children under 2yrs of age, has an increased mortality. “blackbox warning”.