This is an over the counter product - it does not require prescription.
Chlorpheniramine maleate has several important effects and thus several uses.
Most obviously, this medication is an antihistamine and it is used for acute
inflammatory and allergic conditions such as:
Chlorpheniramine maleate is frequently included in antihistamine trials for
allergic skin disease. It is not one of the more effective antihistamines in
dogs but is one of the most reliably effective antihistamines in the cat (in one
study 73% of itchy cats responded). Its availability and inexpensiveness make it
worth trying in many cases.
Mast cell tumors are tumors involving cells that contain granules of
histamine. Patients with mast cell tumors experience chronic inflammatory
symptoms due to circulating histamine. Antihistamines such as chlorpheniramine
maleate may be helpful given long term.
Chlorpheniramine maleate has a strong anti-nausea side effect, which makes it
helpful in treating motion sickness.
Chlorpheniramine maleate causes drowsiness in animals just as it does in
people and can be used as a mild tranquilizer. Some argue that it is the
drowsiness side effect that makes this medication appear to be helpful in itch
management (i.e., patients scratch less because they are sleeping
Convenient dosing makes it a common choice in the cat. It is often used in
the management of feline asthma though its effectiveness in this condition is
Chlorpheniramine maleate is typically administered 2 to 3 times daily.
Histamine is an inflammatory biochemical that causes skin redness, swelling,
pain, increased heart rate, and blood pressure drop when it binds to one of many
H1 receptors throughout the body. Histamine is a very important mediator of
allergy in humans, hence a spectacular array of different antihistamines has
proliferated. Histamine, perhaps unfortunately, is not as important a mediator
of inflammation in pets which means results of antihistamine therapy are not as
reliable in pets.
With so many possible uses of this medication, it is difficult to separate out a
side effect from a primary effect. Drowsiness is generally regarded as an
undesirable side effect.
At doses higher than the recommended dose, human patients complain of dry
mouth and experience difficulty with urination. Animal patients experiencing dry
mouth may drink more water.
Chlorpheniramine maleate is famous for bitter taste. Often the pet
(especially cats) will tolerate the medication for a period of time but
ultimately refuse to take it or even show salivation in response to
administration. In such cases, it may be best to try a different medication.
INTERACTIONS WITH OTHER MEDICATIONS
In the treatment of allergic skin disease, antihistamines are felt to synergize
with omega 3 fatty acid supplements and, as a general rule for this condition,
it is best to use these medications together.
Chlorpheniramine maleate should not be used with additional tranquilizing
This antihistamine is used in an assortment of human products where it is
combined with pain relievers and antihistamines. These combination products
should not be used in animals.
CONCERNS AND CAUTIONS
When using an antihistamine to prevent an allergic reaction (such as a vaccine
reaction) the antihistamine works best when given prior to the allergen.
This medication will interfere with allergic skin testing. Check with your
veterinary dermatologist regarding how far in advance this medication should be
Contraindications: hypersensitivity. Caution: narrow angle glaucoma,
hypertension, GI or urinary obstruction, hypertension, hyperthyroidism,
In humans, the FDA categorizes this drug as category
B for use during
pregnancy (Animal studies have not yet demonstrated risk to the fetus, but
there are no adequate studies in pregnant women; or animal studies have shown an
adverse effect, but adequate studies in pregnant women have not demonstrated a
risk to the fetus in the first trimester of pregnancy, and there is no evidence
of risk in later trimesters.)
It is unknown if chlorpheniramine is excreted into milk; use with caution in
dams nursing neonates.
Most commonly seen adverse effects are CNS depression (lethargy, somnolence)
and GI effects (diarrhea, vomiting, anorexia). The sedative effects of
antihistamines may diminish with time. Anticholinergic effects (dry mouth,
urinary retention) are a possibility.
The sedative effects of antihistamines may adversely affect the performance
of working dogs.
Chlorpheniramine may cause paradoxical excitement in cats. Palatability is
also an issue with this drug and felines.
Overdosage may cause CNS stimulation (excitement to seizures) or depression
(lethargy to coma), anticholinergic effects, respiratory depression, and death.
Treatment consists of emptying the gut if the ingestion was oral using standard
protocols. Induce emesis if the patient is alert and CNS status is stable.
Administration of a saline cathartic and/or activated charcoal may be given
after emesis or gastric lavage. Treatment of other symptoms should be performed
using symptomatic and supportive therapies. Phenytoin (IV) is recommended in the
treatment of seizures caused by antihistamine overdoses in humans; barbiturates
and diazepam are avoided.
Increased sedation can occur if chlorpheniramine is combined with
CNS depressant drugs.
Antihistamines may partially counteract the anticoagulation effects of
Antihistamines can decrease the wheal and flare response to antigen skin
testing. In humans, it is suggested that antihistamines be discontinued at
least 4 days before testing.
Note: Contents of sustained-release capsules may be placed on food, but
should not be allowed to dissolve before ingestion.
1. 4-8 mg (maximum of 0.5 mg/kg) PO q8-12h PO; many clinicians use as
adjunctive treatment of chemotherapy of mast cell tumors
2. 4-12 mg (total dose) bid-tid
Itchy Skin Allergies: As a trial for pruritus
in atopic dogs: 0.4-0.8 mg/kg bid-tid (0.18-0.36 mg/lb 2-3 times a day)
4. As a mild sedative: 0.22 mg/kg PO q8h; 4-20 mg (total dose per day)
1. 2-4 mg per cat q12h PO
2. 2-4 mg per cat q12-24h PO
3. Most common dosage in cats is: 2 mg per cat
4. For pruritus: 2-4 mg/ cat twice daily; rarely may be maintained on once
daily dosing. Palatability may be enhanced by dipping the split tablet into tuna
fish "juice", butter or petrolatum; placing split tablets into empty gelatin
capsules or sprinkling or mixing timed release beads (partial contents of an 8
mg capsule) with food.
5. As a mild sedative: 1-2 mg per cat q12-24h (low dose), 2-4 mg/cat PO
q12-24h (high dose)
1. 1-2 mg/kg PO 2-3 times a day
Chlorpheniramine tablets and sustained-release capsules should be stored in
tight containers. The sustained-release tablets should be stored in well-closed
containers. The oral solution should be stored in light-resistant containers;
avoid freezing. All chlorpheniramine products should be stored at room
Chlorpheniramine maleate is available in 2 mg, 4 mg, 8 mg & 12 mg tablets as
well as oral syrup and injectable.