chlorpheniramine

Chlorpheniramine is an over-the-counter medication used to relieve symptoms of colds and allergies including sneezing, runny nose, itchy and watery eyes. Chlorpheniramine is a first generation antihistamine that can easily cross the blood-brain barrier, causing drowsiness as a side effect, which the second generation antihistamines do not cause.

Chlorpheniramine works by blocking the activity of histamine, a natural compound in the body that causes allergy symptoms. Histamine is released by mast cells and basophils, types of immune cells, in response to allergen exposure. Chlorpheniramine binds to histamine H1 receptors in blood vessels, respiratory tract, and gastrointestinal tract, preventing their activation by histamine and the resultant allergic reaction.

Chlorpheniramine may be used for symptom relief in the following conditions:

• Perennial and seasonal allergic rhinitis
• Perennial and seasonal vasomotor rhinitis
• Allergic conjunctivitis
• Common colds
• Hives (urticaria)
• Itching (pruritus)
• Swelling of tissue under the skin and mucous membranes (angioedema)
• Severe allergic reactions (anaphylactic reactions) such as swelling of throat, difficulty breathing, drop in blood pressure, dizziness, and fainting.

• Do not use chlorpheniramine to treat:
  • Patients who are hypersensitive to chlorpheniramine or any of its components
  • Individuals with lower respiratory disease such as asthma (controversial)
  • Patients with sleep apnea
  • Premature babies and newborns
• Avoid using chlorpheniramine in nursing mothers
• Use chlorpheniramine with caution in the following conditions:
  • Narrow angle glaucoma
  • Prostatic hypertrophy
  • Stenosing peptic ulcer
  • Pyloroduodenal obstruction
  • Bladder neck obstruction

Common side effects of chlorpheniramine include:

• Central nervous system depression
• Sedation ranging from mild drowsiness to deep sleep (most frequent)
• Dizziness
• Lack of energy (lassitude)
• Impaired coordination
• Muscular weakness
• Restlessness
• Faintness
• Insomnia
• Euphoria
• Nervousness
• Irritability
• Delirium
• Abnormal skin sensation (paresthesia)
• Tremors
• Seizures (less common)
• Balance disorder (labyrinthitis)
• Ringing in the ears (tinnitus)
• Vertigo
• Visual disturbances
• Double vision (diplopia)
• Dryness of nose, mouth and throat
• Thickening of bronchial secretions
• Wheezing
• Nasal stuffiness
• Sweating
• Chills
• Involuntary facial movements (facial dyskinesia)
• Headache
• Tightness of the chest
• Palpitations
• ECG changes
• Rapid heartbeat (tachycardia)
• Irregular heart rhythm (arrhythmia)
• High or low blood pressure (hypertension/hypotension)
• Greater incidence of dizziness, sedation, and hypotension in elderly patients
• Upper abdominal (epigastric) distress
• Loss of appetite (anorexia)
• Nausea
• Vomiting
• Diarrhea
• Constipation
• Impaired bile flow (cholestasis)
• Abnormal liver function
• Liver inflammation (hepatitis)
• Liver failure
• Jaundice (rare)
• Painful urination (dysuria)
• Urinary retention
• Impotence
• Early menstrual periods
• Blood disorders such as:
  • Anemia from rapid destruction of red cells (hemolytic anemia)
  • Low levels of leukocytes, a type of immune cell (leukopenia)
  • Low levels of granulocytes, immune cells with granules (agranulocytosis)
  • Low platelet count (thrombocytopenia)
  • Low count of all types of blood cells (pancytopenia)

This is not a complete list of all side effects or adverse reactions that may occur from the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may also report side effects or health problems to the FDA at 1-800-FDA-1088.

Tablet

• 4 mg
• 8 mg
• 12 mg

Syrup

• 2 mcg/5 mL

Suspension (pediatric only)

• 2 mg/mL

Adult

Allergic Rhinitis

• Tablets or syrup: 4 mg orally every 4-6 hours; not to exceed 24 mg/day
• Extended-release tablets: 8 mg orally every 8-12 hours or 12 mg every 12 hours; not to exceed 24 mg/day
• Extended-release capsules: 12 mg orally once/day; not to exceed 24 mg/day
• Sustained-release capsules: 8-12 mg orally every 8-12 hours, up to 16-24 mg/day

Pediatric

• Children under 2 years: Safety and efficacy not established
• Children 2-6 years: 1 mg orally every 4-6 hours; not to exceed 6 mg/day
• Children 6-12 years: 2 mg orally every 4-6 hours; not to exceed 12 mg/day or sustained release at bedtime
• Children over 12 years:
  • Tablets or syrup: 4 mg orally every 4-6 hours; not to exceed 24 mg/day
• Extended-release tablets: 8 mg orally every 8-12 hours or 12 mg every 12 hours; not to exceed 24 mg/day
• Extended-release capsules: 12 mg orally once/day; not to exceed 24 mg/day
• Sustained-release capsules: 8-12 mg orally every 8-12 hours, up to 16-24 mg/day

Geriatric

• 4 mg orally once/day or every 12 hours
• Sustained-release: 8 mg orally at bedtime

Inform your doctor of all medications you are currently taking, who can advise you on any possible drug interactions. Never begin taking, suddenly discontinue, or change the dosage of any medication without your doctor’s recommendation.

• Chlorpheniramine has no known severe interactions with other drugs.
• Serious interactions of chlorpheniramine include:
  • eluxadoline
  • idelalisib
  • isocarboxazid
  • ivacaftor
  • sodium oxybate
  • tranylcypromine
• Chlorpheniramine has moderate interactions with at least 201 different drugs.
• Mild interactions of chlorpheniramine include:
  • ashwagandha
  • brimonidine
  • eucalyptus
  • nettle
  • sage
  • Siberian ginseng

The drug interactions listed above are not all of the possible interactions or adverse effects. For more information on drug interactions, visit the RxList Drug Interaction Checker.

It is important to always tell your doctor, pharmacist, or health care provider of all prescription and over-the-counter medications you use, as well as the dosage for each, and keep a list of the information. Check with your doctor or health care provider if you have any questions about the medication.

• Chlorpheniramine use during pregnancy is recommended only when potential benefit outweighs potential risk. There is no controlled data for chlorpheniramine use in pregnancy, however, antihistamine exposure in first trimester is not reported to be associated with increased risk of malformations.
• Chlorpheniramine is excreted in breast milk. Small, occasional doses of the drug is acceptable during breastfeeding. Large doses or prolonged use, particularly before nursing for the first time, may reduce milk production, and may cause effects in the infant.

In geriatric treatment:

• Non-anticholinergic antihistamines should be considered first when treating allergic reactions (Beers Criteria). Anticholinergic antihistamines block the activity of a neurotransmitter known as acetylcholine, which can affect involuntary muscle function and fluid secretions
• Avoid use of chlorpheniramine in the elderly because of the high incidence of anticholinergic effects
• Drug clearance is reduced with advanced age and poses a greater risk of confusion, dry mouth, constipation, and other anticholinergic effects and toxicity
• Chlorpheniramine may exacerbate existing lower urinary conditions or prostate enlargement (benign prostatic hyperplasia)