Pheniramine (most famous brand name ‘Avil’) is an H1 antihistamine, used to treat acute allergic conditions such as insect bite/sting, drug allergy, blood transfusion reaction etc. it is moderately sedative and produces other CNS side effects, as crosses blood-brain barrier.
Drug class
H1 antihistamine, 1st generation
Available preparations
pheniramine maleate
- Tablet: 25 mg, 50 mg
- Syrup: 15 mg/5 ml (not marketed now because of drug abusing)
- Parenteral: 22.5 mg/ml injection
* Pheniramine has withdrawn from market in some countries like U.S.
Dosage
- Adult: 25 – 50 mg Oral or I.M. (single dose or once daily I.M./ I.V.)
- Children: 15 – 30 mg (3 mg/kg/dose) Oral/I.M. (single dose or once daily)
Common uses
- Acute drug allergy
- Blood transfusion reaction
- Allergy due to insect bite/sting
- Pruritis
- Oedematous lesions of serum sickness
- Urticaria and atopic contact dermatitis
* Pheniramine is mostly co-administered with corticosteroids for acute allergic conditions.
Side effects
Due to H1 antihistaminic action-
- Sedation
- Decreased alertness and concentration
- Mild headedness
- Increased appetite
- Motor incoordination
- Fatigue and tendency to fall asleep
Due to anticholinergic action-
- Dryness of mouth
- Urinary hesitancy
- Alteration of bowel
- Blurring of vision
Overdose or acute toxicity produce symptoms similar to atropine poisoning. These includes hallucinations, excitement, ataxia, incoordination, and convulsions, dilated pupils with a flushed face, together with sinus tachycardia, urinary retention, dry mouth, and fever.
It excreted in small amounts in breast milk. If taken by lactating mothers, it may cause symptoms such as irritability, drowsiness, or respiratory depression in the nursing infant.
Pharmacological characteristics
- Onset of action: 15-30 minutes
- Half-life (t1/2): 8-17 hours (I.V.), 16-19 hours (Oral)
- Duration of action: 24-72 hours
- Additional antimuscarinic action
- Pheniramine has strong membrane stabilizing property, but not used clinically as local anesthetic because it causes irritation on subcutaneous injection.