Chlorpheniramine Maleate
Chlorpheniramine maleate is a first-generation H1 antihistamine used for symptomatic management of selected allergic conditions in dogs and cats. It has a long history of empirical veterinary use, particularly for pruritic skin disease in cats. The response depends on how much histamine contributes to the individual patient’s clinical signs.
Group
First-generation H1 antihistamine
Mechanism of Action
Chlorpheniramine inhibits signaling at histamine H1 receptors on blood vessels, sensory nerves and other effector tissues. This reduces histamine-mediated capillary leakage, swelling and stimulation of itch pathways. It acts on the tissue response to histamine rather than preventing histamine release. Central H1-receptor activity and additional antimuscarinic effects contribute to its broader pharmacologic profile.
Dose Rates
Dogs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Allergic signs | Reference only | PO | 4–8 mg per dog orally every 12 hours, but no more than 0.5 mg/kg per dose. Both constraints must be applied; the schema cannot encode a per-kg cap against a fixed amount. | |
| Allergic signs with fixed-dose ceiling | Reference only | PO | Additional alternatives: 4–8 mg orally every 8–12 hours or 2–8 mg every 12 hours, each subject to a maximum of 0.5 mg/kg per dose. The two constraints require a dedicated capped fixed-dose calculation. | |
| Alternative allergic-sign treatment | 4–12 mg/animal | PO | Every 8–12 h | Separate historical alternative; do not combine with capped fixed-dose instructions from another regimen. |
| Atopic pruritus trial | Reference only | PO | Historical trial alternatives are 0.4–0.8 mg/kg or 0.2–0.8 mg/kg two to three times daily; those bullets do not explicitly assign a route. They differ from the lower fixed-dose capped regimens. | |
| Mild sedation | 0.22 mg/kg | PO | Every 8 h |
Cats
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Allergic signs | 2 mg/animal | PO | Every 12 h | |
| Allergic signs | 2–4 mg/animal | PO | Every 12–24 h | |
| Allergic signs | 2 mg/animal | PO | Every 8–12 h | |
| Pruritus | 2–4 mg/animal | PO | Every 12 h | Some cats can be maintained once daily after control. |
| Mild sedation | 1–2 mg/animal | PO | Every 12–24 h | |
| Higher-dose mild sedation | 2–4 mg/animal | PO | Every 12–24 h |
Ferrets
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Allergic signs | 1–2 mg/kg | PO | Every 8–12 h |
Birds
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Drinking-water medication | Reference only | PO | One 4 mg tablet in 240 mL drinking water, changed daily. Delivered mg/kg depends on water consumption and cannot be calculated as a fixed bird dose. |
Indications
- Adjunctive symptomatic relief of allergic pruritus in dogs and cats, with variable and often limited clinical response.
- Symptomatic treatment of histamine-associated urticaria and other cutaneous allergic reactions in dogs and cats.
Contraindications
- Glaucoma, ileus or cardiac arrhythmias where antimuscarinic activity is undesirable.
- Urinary outflow or pyloroduodenal obstruction, prostatic enlargement and secretion-sensitive lower-airway disease require caution.
- Use cautiously with hyperthyroidism, cardiovascular disease or hypertension.
Interactions
- No veterinary interactions are identified in the supplied material.
Adverse effects
- Sedation
- Dry mouth and reduced gastrointestinal secretion
Preparations
| Preparation | Form | Strength | Route |
|---|---|---|---|
| Chlorpheniramine Maleate 2 mg tablet | Tablet | 2 mg / tablet | PO |
| Chlorpheniramine Maleate 4 mg tablet | Tablet | 4 mg / tablet | PO |
| Chlorpheniramine Maleate 8 mg tablet | Tablet | 8 mg / tablet | PO |
| Chlorpheniramine maleate syrup 2 mg/5 mL | Oral Liquid | 2 mg / 5 mL | PO |
Monitoring and Administration
Avoid substituting combination cold or cough remedies that contain other active ingredients.
The dog fixed dose is limited by a simultaneous weight-based ceiling: do not exceed 0.5 mg/kg per dose. The current schema cannot encode this cap against a fixed-dose regimen.
Protect oral liquid from freezing.
The source’s feline 0.5–2 mg example does not agree with its stated quarter-to-half of a 4 mg tablet (1–2 mg); this inconsistent example is not used for calculation.
Sustained-release beads must remain intact; placing intact beads in food does not justify crushing or dissolving them.