chlorpheniramine (OTC)

Varies in incidence & severity with the individual drug; also individual patients vary in susceptibility

Frequency Not Defined

CNS depression

Drowsiness

Sedation ranging from mild drowsiness to deep sleep (most frequent)

Dizziness

Lassitude

Disturbed coordination

Muscular weakness

Restlessness, insomnia, tremors, euphoria, nervousness, delirium, palpitation, seizures is less common

Epigastric distress

Anorexia

Nausea

Vomiting

Diarrhea

Constipation

Cholestasis, hepatitis, hepatic failure, hepatic function abnormality, jaundice is rare

Tachycardia, palpitation ECG changes (eg, widened QRS)

Arrhythmias (eg, extrasystole, heart block)

Hypotension

Hypertension

Dizziness, sedation, and hypotension may occur in geriatric patients

Dryness of mouth, nose, and throat

Dysuria

Urinary retention

Impotence

Vertigo

Visual disturbances

Blurred vision

Diplopia; tinnitus

Acute labyrinthitis

Insomnia

Tremors

Nervousness

Irritability

Facial dyskinesia

Tightness of the chest

Thickening of bronchial secretions

Wheezing

Nasal stuffiness

Sweating

Chills

Early menses

Toxic psychosis

Headache

Faintness

Paresthesia

Agranulocytosis

Hemolytic anemia

Leukopenia

Thrombocytopenia

Pancytopenia

Contraindications

Documented hypersensitivity

Lower respiratory disease, eg, asthma (controversial)

Preemies & neonates

Nursing women

Acute asthma, sleep apnea

Cautions

Caution in narrow angle glaucoma, prostatic hypertrophy, stenosing peptic ulcer, pyloroduodenal obstruction, or bladder neck obstruction

Chlor Trimeton non-drowsy contains no chlorpheniramine, only pseudoephedrine

All injections discontinued

Pregnancy

Antihistamine exposure in first trimester not reported to be associated with increased risk of malformations; animal studies not reported; there are no controlled data in human pregnancy; only recommended for use during pregnancy when benefit outweighs risk

Lactation

Excretion into human milk; the manufacturer recommends that caution be used when administering chlorpheniramine to nursing women; infants should be monitored for irritability or drowsiness; antihistamines may temporarily decrease maternal serum prolactin concentrations when administered prior to nursing infant for the first time

Pregnancy Categories

A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

NA: Information not available.

Mechanism of Action

Histamine H1-receptor antagonist in blood vessels, respiratory tract, and gastrointestinal tract

Pharmacokinetics

Half-Life elimination: 10-13 hr (children); 14-24hr (adult)

Duration: 24 hr

Peak Plasma Time: 2-3 hr (range 1-6 hr)

Protein Bound: 29-37%

Vd: 4-7 L/kg (children); 6-12 L/kg (adults)

Metabolism: Liver (CYP2D6)

Metabolites: Monodesmethylchlorpheniramine, didesmethylchlorpheniramine

Excretion: Urine

Sedative effect: Low

Antihistamine activity: Moderate

Anticholinergic acitivity: Moderate

Parenteral forms discontinued

IV Compatibilities

Additive: amikacin, calcium chloride, kanamycin, norepinephrine, pentobarbital

Syringe: diatrizoate meglumine, diatrizoate sodium, iodipamide meglumine, iothalamate meglumine, iothalamate sodium

IV/IM Administration

Administer SC/IM/IV injection over 1 min

100 mg/mL injection should not be given IV

Storage

Store at 25C

Protect from light