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Chlorpheniramine Maleate/Phenylephrine Hydrochloride/Methscopolamine Nitrate

Pronouncation: (klor-fen-AIR-uh-meen MAL-ee-ate/Fen-ill-EFF-rin HIGH-droe-KLOR-ide/meth-skoe-PAHL-uh-meen NYE-trate)
Class: Antihistamine, Decongestant, Anticholinergic

Trade Names:
AH-chew
- Tablets 10 mg phenylephrine, 2 mg chlorpheniramine, 1.25 mg methscopolamine

Trade Names:
Dallergy
- Syrup 10 mg phenylephrine, 2 mg chlorpheniramine, 0.625 mg methscopolamine
- Tablets 10 mg phenylephrine, 4 mg chlorpheniramine, 1.25 mg methscopolamine
- Tablets 20 mg phenylephrine, 12 mg chlorpheniramine, 2.5 mg methscopolamine

Trade Names:
Dehistine
- Syrup 10 mg phenylephrine, 2 mg chlorpheniramine, 1.25 mg methscopolamine

Trade Names:
DriHist
- SR Tablets 20 mg phenylephrine, 8 mg chlorpheniramine, 2.5 mg methscopolamine

Trade Names:
Duradryl
- Syrup 10 mg phenylephrine, 2 mg chlorpheniramine, 1.25 mg methscopolamine

Trade Names:
Ex-Histine
- Syrup 10 mg phenylephrine, 2 mg chlorpheniramine, 1.25 mg methscopolamine

Trade Names:
Extendryl
- Chewable Tablets 10 mg phenylephrine, 2 mg chlorpheniramine, 1.25 mg methscopolamine
- SR Capsules 20 mg phenylephrine, 8 mg chlorpheniramine, 2.5 mg methscopolamine
- Syrup 10 mg phenylephrine, 2 mg chlorpheniramine, 1.25 mg methscopolamine

Trade Names:
Hista-Vent DA
- Tablets 20 mg phenylephrine, 8 mg chlorpheniramine, 2.5 mg methscopolamine

Trade Names:
Omnihist L.A.
- Tablets 20 mg phenylephrine, 8 mg chlorpheniramine, 2.5 mg methscopolamine

Trade Names:
Pre-Hist-D
- Tablets 20 mg phenylephrine, 8 mg chlorpheniramine, 2.5 mg methscopolamine

Mechanism of Action

Pharmacology

Chlorpheniramine

Competitively antagonizes histamine at H 1 receptor sites.

Slideshow: 2014 Update: First Time Brand-to-Generic Switches

Phenylephrine

Stimulates postsynaptic alpha-receptors, resulting in vasoconstriction, which reduces congestion.

Methscopolamine

Competitively inhibits action of acetylcholine at muscarinic receptors.

Indications and Usage

Temporary relief of symptoms of allergic rhinitis, vasomotor rhinitis, sinusitis, and the common cold.

Contraindications

Hypersensitivity or idiosyncratic reaction to any ingredients of product; severe hypertension; severe coronary artery disease; narrow-angle glaucoma; urinary retention; hyperthyroidism; peptic ulcer; asthma attack; MAO inhibitor therapy or for 2 wk after stopping MAO inhibitor therapy.

Dosage and Administration

Extended-Release Formulations
Adults and Children (12 yr and older)

PO 1 tablet/capsule q 12 hr.

Children 6 to 12 yr

PO ½ tablet/capsule q 12 hr.

Chewable Tablets
Adults and Children (12 yr and older)

PO 1 to 2 tablets q 4 hr.

Children 6 to 12 yr

PO 1 tablet q 4 hr.

Children less than 6 yr

PO As recommended by health care provider.

Syrup
Adults

PO 1 to 2 tsp (5 to 10 mL) q 3 to 4 hr.

Children 6 to 12 yr

PO ½ to 1 tsp (2.5 to 5 mL), depending on weight of child; may repeat q 4 hr.

Children less than 6 yr

PO As recommended by health care provider.

PreHist-D / Hista-Vent DA
Adults and children 12 yr and older

PO 1 tablet q 12 hr.

Children 6 to 12 yr

PO ½ tablet q 12 hr.

General Advice

Syrup
  • Give with food or milk if GI upset occurs.
  • Use dosing spoon or syringe for pediatric doses of syrup.
Chewable tablets

Give with food or milk if GI upset occurs.

Extended-release formulations
  • Caplets may be broken in half but should not be crushed or chewed.
  • Give with food or milk if GI upset occurs.

Storage/Stability

Syrup

Store at controlled room temperature. Keep syrup tightly capped and protect from freezing.

Chewable tablets

Store at controlled room temperature (69° to 77°F).

Extended-release formulations

Store at controlled room temperature (69° to 77°F).

Drug Interactions

Alcohol, barbiturates (eg, phenobarbital), tricyclic antidepressants (eg, amitriptyline), other CNS depressants

Effects may be enhanced by chlorpheniramine.

MAO inhibitors (eg, isocarboxazid)

May prolong and intensify the effects of chlorpheniramine and increase the effects of phenylephrine.

Mecamylamine, methyldopa, reserpine, veratrum alkaloids

Antihypertensive effects may be reduced by phenylephrine.

Laboratory Test Interactions

May interfere with diagnostic test results for skin tests using allergen extracts.

Adverse Reactions

Cardiovascular

Phenylephrine

Tachycardia; palpitations; arrhythmias; cardiovascular collapse; hypotension.

CNS

Chlorpheniramine

Drowsiness; dizziness.

Phenylephrine

Nervousness; insomnia; restlessness; headache; fear; anxiety; tremor; weakness; insomnia; hallucinations; convulsions; CNS depression; irritability; tenseness.

Dermatologic

Phenylephrine

Pallor.

EENT

Chlorpheniramine

Blurred vision; nose, throat, and mouth dryness.

GI

Phenylephrine

Gastric irritation and irritability.

Genitourinary

Chlorpheniramine

Urinary retention.

Phenylephrine

Dysuria; urinary retention.

Respiratory

Phenylephrine

Respiratory difficulty.

Precautions

Monitor

Allergy symptoms

Assess for allergy symptoms (eg, rhinitis, nasal congestion, sneezing, itching, watery eyes) before and periodically throughout therapy.

CNS symptoms

Monitor patient for nervousness, dizziness, and insomnia. If noted, hold therapy and notify health care provider.

Excitability

Monitor children for antihistamine-induced excitability.


Pregnancy

Category C .

Lactation

Undetermined.

Children

Safety and efficacy in children less than 6 yr not established. Antihistamines may cause excitability in children.

Elderly

Patients 60 yr and older more likely to exhibit adverse effects.

Special Risk Patients

Use with caution in patients with hypertension, heart disease, asthma, hyperthyroidism, increased IOP, diabetes mellitus, and prostatic hypertrophy.

Overdosage

Symptoms

Dry mouth, dilated pupils, hallucinations, severe hypertension, ventricular extrasystoles, short paroxysms of ventricular tachycardia, CNS depression, CNS stimulation, somnolence, convulsions, shock, death.

Patient Information

  • Review dosing schedule for prescribed dose form (eg, syrup, chewable tablet, extended-release tablet).
  • Advise caregiver to use dosing spoon or syringe when giving syrup to children.
  • Caution patient that extended-release tablet can be broken in half but that dose should be swallowed whole and not crushed or chewed.
  • Advise patient to take with food or milk if GI upset occurs.
  • Advise patient to take last dose late in the afternoon or early evening to reduce chance of drug causing sleeplessness.
  • Advise patient that if a dose is missed to take as soon as remembered unless it is nearing time for the next dose. Caution patient to not double the dose to catch up.
  • Advise patient that if allergy symptoms are not controlled, not to increase the dose of medication but to inform health care provider.
  • Caution patient that drug may cause drowsiness and to use caution while driving or performing other tasks requiring mental alertness until tolerance is determined.
  • Advise patient to avoid alcohol and other CNS depressants because of risk of excessive sedation.
  • Caution patient not to take any OTC antihistamines or decongestants while taking this medication unless advised by health care provider.
  • If patient is to have allergy skin testing, advise to not take the medication for at least 6 days before the skin testing.
  • Instruct patient to stop taking drug and immediately report any of the following symptoms to health care provider: nervousness, dizziness, sleeplessness.
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