Skip to Content

The originating document has been archived. We cannot confirm the completeness, accuracy and currency of the content.

Phenylephrine Hydrochloride / Guaifenesin

Pronunciation: Fen-ill-EFF-rin HIGH-droe-KLOR-ide /GWHY-fen-ah-sin
Class: Decongestant, Expectorant

Trade Names

- Capsules phenylephrine hydrochloride 10 mg/guaifenesin 390 mg

- Liquid phenylephrine hydrochloride 5 mg/guaifenesin 100 mg

- Liquid phenylephrine hydrochloride 7.5 mg/guaifenesin 100 mg

Entex ER
- Capsules, extended-release phenylephrine hydrochloride 10 mg/guaifenesin 300 mg

Entex LA
- Capsules, extended-release phenylephrine hydrochloride 30 mg/guaifenesin 600 mg

Entex LQ
- Liquid phenylephrine hydrochloride 10 mg/guaifenesin 100 mg per 5 mL

GFN 600/Phenylephrine 20
- Tablets phenylephrine hydrochloride 20 mg/guaifenesin 600 mg

- Capsules phenylephrine hydrochloride 15 mg/guaifenesin 400 mg

- Capsules phenylephrine hydrochloride 7.5 mg/guaifenesin 200 mg

- Tablets, extended-release phenylephrine hydrochloride 40 mg/guaifenesin 650 mg

- Tablets, extended-release phenylephrine hydrochloride 20 mg/guaifenesin 315 mg

PE/GG 7.5/100
- Liquid phenylephrine hydrochloride 7.5 mg/guaifenesin 100 mg

- Liquid phenylephrine hydrochloride 5 mg/guaifenesin 100 mg

- Tablets phenylephrine hydrochloride 15 mg/guaifenesin 600 mg



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


May enhance output of respiratory tract fluid by reducing adhesiveness and surface tension, enhancing removal of viscous mucus and making nonproductive coughs more productive and less frequent.

Indications and Usage

Temporary relief of symptoms of upper respiratory tract disorders such as sinusitis, vasomotor rhinitis, and hay fever; temporary relief of coughs associated with respiratory tract infections and related conditions such as sinusitis, pharyngitis, bronchitis, and asthma when tenacious mucus and/or mucus plugs and congestion complicate these conditions.


Hypersensitivity to any component of product; hypersensitivity or idiosyncrasy to sympathomimetic amines, which may manifest by insomnia, dizziness, weakness, tremor, or arrhythmias. Hypertension; ventricular tachycardia; severe coronary artery disease; hyperthyroidism; patients on monoamine oxidase inhibitor (MAOI) therapy and for 14 days after stopping MAOI therapy; infants and newborns.

Dosage and Administration

See prescribing information for specific dosing information:

Maximum dose

The following maximum doses are according to the prescribing information.

Adults and Children 12 y of age and older

Phenylephrine 60 mg/day; guaifenesin 2,400 mg/day.

Children 6 to 11 y of age

Phenylephrine 30 mg/day; guaifenesin 1,200 mg/day.

Children 2 to 5 y of age

Phenylephrine 15 mg/day; guaifenesin 150 mg/day.

Adults and Children (12 y of age and older) Upper respiratory tract disorders

For specific dosing by product, refer to the manufacturer's prescribing information.

Capsules, ER

PO 1 or 2 every 12 h.


PO 5 to 10 mL every 4 to 6 h.

Tablets, ER

PO 1 or 2 every 12 h.

Children 6 to 12 y of age Capsules, ER

PO 1 every 12 h.


PO 2.5 to 5 mL every 4 to 6 h.

Tablets, ER

PO ½ to 1 every 12 h.

Children 2 to 5 y of age ( Entex LQ only)

PO 1.25 mL every 4 h.


Patients 60 y of age and older are more likely to experience adverse sympathomimetic effects.

General Advice

  • Give with food if GI upset occurs.
  • Take with a full glass of water (240 mL).
  • Tablets may be broken in half for ease of administration. Do not crush or chew tablets or half-tablets.
  • Do not exceed recommended dosage.


Store between 59° and 86°F.

Drug Interactions

Beta-adrenergic blockers, MAOIs

May potentiate the pressor effect of phenylephrine. Concurrent use or use within 14 days after stopping an MAOI is contraindicated.

Digitalis glycosides, other vasopressor drugs during halothane anesthesia

The risk of cardiac arrhythmias may be increased.

Guanethidine, mecamylamine, methyldopa, reserpine, veratrum alkaloids

Hypotensive effects of these agents may be reduced.

Tricyclic antidepressants

Effects of phenylephrine may be decreased.

Laboratory Test Interactions

Guaifenesin may interfere with the interpretation of the test for urinary 5-hydroxyindoleacetic acid for the diagnosis of carcinoid syndrome; VMA test for catecholamines may be falsely elevated; guaifenesin may increase renal Cl for urate and thereby lower serum uric acid levels.

Adverse Reactions


Tachycardia; palpitations; arrhythmias; CV collapse with hypotension.


Headache; dizziness; fear; anxiety; nervousness; restlessness; tremor; weakness; insomnia; hallucinations; convulsions; CNS depression; CNS stimulation; excitability; drowsiness; light-headedness; tenseness.


Nausea; vomiting.


Dysuria, pallor, respiratory difficulty.



Category C .


Small amounts of phenylephrine excreted in breast milk.


Not recommended for use in children younger than 6 y of age; consult a heath care provider before use in children 12 y of age and younger ( Deconex ); consult a health care provider before using in children younger than 2 y of age ( Entex LQ ).


Patients 60 y of age and older are more likely to experience adverse sympathomimetic effects. Use extreme caution.

Special Risk Patients

Use extreme caution in patients with bradycardia, partial heart block, myocardial disease, or severe arteriosclerosis. Use with caution in patients with hypertension, heart disease, asthma, thyroid disease, increased IOP, diabetes mellitus, prostatic hypertrophy, difficulty in urination due to enlargement of the prostate gland.

Chronic cough

Advise patients not to take for persistent or chronic cough that occurs, such as one that occurs with smoking, asthma, or emphysema, or if the cough is accompanied by excessive phlegm, unless directed by a health care provider.

Drug abuse

Has abuse potential.



Cardiac arrhythmias, cerebral hemorrhage, pulmonary edema, palpitation, tremor, dizziness, vomiting, fear, labored breathing, headache, dryness of mouth, pallor, weakness, panic, anxiety, confusion, hallucinations, delirium, restlessness, hyperactive reflexes, talkativeness, irritability, insomnia, difficulty in urination, flushing, hypertension with subsequent hypotension, circulatory collapse.

Patient Information

  • Advise patient that tablets may be broken in half for ease of administration.
  • Instruct patient to not chew or crush tablets or half-tablets and to swallow whole.
  • Advise patient to take with food if GI upset occurs.
  • 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.
  • Instruct patient to discontinue use and report any of the following symptoms to health care provider: nervousness, dizziness, sleeplessness; persistent or recurrent cough; cough associated with fever, rash, or persistent headache; bothersome adverse reactions.
  • Advise patient that if symptoms are not controlled, not to increase the dose of medication but to inform health care provider.
  • Caution patient not to take MAOIs while taking this medication.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.