Pheniramine maleate is a first-generation (classical) ethanolamine-derivative antihistamine with pronounced sedative and anticholinergic properties. The 22.75mg strength is a common oral tablet formulation in India, equivalent to 15mg of the pheniramine base. It is primarily used for symptomatic relief of allergic conditions, pruritus, and as a sedative in various over-the-counter (OTC) and prescription combinations.
Adult: 22.75mg (one tablet) every 4 to 6 hours. Maximum: 4 tablets (91mg) in 24 hours. Often used as a single dose at night for sedation.
Note: Oral administration. Can be taken with or without food. Taking with food may reduce GI upset. Tablet should be swallowed whole with a glass of water. Avoid crushing/chewing unless advised (bitter taste).
Competitively and reversibly inhibits histamine at the H1-receptor sites on effector cells in the gastrointestinal tract, blood vessels, and respiratory tract. This blockade prevents histamine-mediated allergic responses such as vasodilation, increased capillary permeability, and bronchoconstriction.
Pregnancy: Category B (US FDA). Animal studies show no risk, but no adequate controlled human studies. Use only if clearly needed, especially in the third trimester (risk of neonatal anticholinergic effects). Avoid in first trimester unless benefit outweighs risk.
Driving: NOT ADVISABLE. Significantly impairs alertness, reaction time, and motor coordination. Patients must be warned not to drive or operate heavy machinery for at least 6-8 hours after a dose, or longer if they feel drowsy.
| Alcohol, Benzodiazepines, Opioids, Barbiturates | Potentiation of CNS depression (additive sedation, impaired psychomotor performance). | Major |
| Monoamine Oxidase Inhibitors (MAOIs) - e.g., Phenelzine, Tranylcypromine | Increased anticholinergic and CNS depressant effects; risk of hypertensive crisis. | Contraindicated |
| Other Anticholinergics (e.g., Atropine, TCAs, Antipsychotics) | Additive anticholinergic toxicity (dry mouth, constipation, urinary retention, confusion, hyperthermia). | Major |
| CNS Stimulants (e.g., Amphetamines) | Mutual antagonism of therapeutic effects. | Moderate |
| Hepatic Enzyme Inhibitors (e.g., Cimetidine, Fluoxetine, Quinidine) | Increased plasma levels and toxicity of pheniramine due to inhibited metabolism (CYP2D6). | Moderate |
Same composition (Pheniramine (22.75mg)), different brands: