Entex La

Last updated on RxList: 6/28/2022

Drug Summary

What Is Entex La?

Entex LA (phenylephrine hydrochloride and guaifenesin) is a combination of a decongestant and an expectorant used to treat stuffy nose and sinus congestion, and to reduce chest congestion caused by the common cold or flu. Entex LA is available in generic form.

What Are Side Effects of Entex La?

Common side effects of Entex LA include:

  • nausea,
  • vomiting,
  • upset stomach,
  • loss of appetite,
  • flushing (warmth, tingling, or redness under the skin),
  • feeling excited or restless (especially in children),
  • sleep problems (insomnia),
  • skin rash or itching,
  • headache, or
  • dizziness.

Tell your doctor if you have serious side effects of Entex LA including:

  • fast, pounding, or uneven heartbeat;
  • severe dizziness, anxiety, restlessness, or nervousness;
  • easy bruising or bleeding, unusual weakness, fever, chills, body aches, flu symptoms;
  • dangerously high blood pressure (severe headache, blurred vision, buzzing in your ears, anxiety, confusion, chest pain, shortness of breath, uneven heartbeats, seizures);
  • stomach pain, loss of appetite, dark urine, clay-colored stools, or yellowing of the skin or eyes.

Seek medical care or call 911 at once if you have the following serious side effects:

  • Serious eye symptoms such as sudden vision loss, blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights;
  • Serious heart symptoms such as fast, irregular, or pounding heartbeats; fluttering in your chest; shortness of breath; and sudden dizziness, lightheartedness, or passing out;
  • Severe headache, confusion, slurred speech, arm or leg weakness, trouble walking, loss of coordination, feeling unsteady, very stiff muscles, high fever, profuse sweating, or tremors.

This document does not contain all possible side effects and others may occur. Check with your physician for additional information about side effects.

Dosage for Entex La

The dose of Entex LA for adults and children 12 years of age and older is:

  • one tablet twice daily (every 12 hours

The pediatric dose for children 6 to 12 years is:

  • 1/2 tablet twice daily (every 12 hours).

What Drugs, Substances, or Supplements Interact with Entex La?

Entex LA may interact with medicines to treat high blood pressure, beta-blockers, or antidepressants. Tell your doctor all medications you use.

Entex La During Pregnancy or Breastfeeding

During pregnancy, Entex LA should be used only if prescribed. This medication passes into breast milk and could harm a nursing baby. Consult your doctor before breastfeeding.

Additional Information

Our Entex LA (phenylephrine hydrochloride and guaifenesin) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

Drug Description


Entex LA (guaifenesin and phenylephrine) is an orange, scored, long-acting tablet for oral administration and contains

phenylephrine hydrochloride ... 30mg

guaifenesin ....................................... 400 mg

in a special base to provide a prolonged therapeutic effect.

This product contains ingredients of the following therapeutic classes: decongestant and expectorant.

Phenylephrine Hydrochloride, a synthetic sympathomimetic agent, is a vasoconstrictor and pressor drug chemically related to epinephrine and ephedrine. Chemically, it is (-)-m-Hydroxy-a-[(methyl amino)methyl] benzyl alcohol hydrochloride. It has the following molecular formula C9H13NO2 · HCl with a molecular weight of 203.67.

Guaifenesin is an expectorant having the chemical name, 1,2-propanediol, 3-(2-methoxyphenoxy)-.

Entex LA (guaifenesin and phenylephrine) Inactive Ingredients: Each tablet contains carbomer 934 P, compressible sugar, docusate sodium, FD&C Yellow No. 6 Aluminum Lake, hydroxypropyl cellulose, hydroxypropyl methylcellulose, polyethylene glycol, silicon dioxide, stearic acid, titanium dioxide, and zinc stearate.

Indications & Dosage


Phenylephrine HCl w/guaifenesin long acting tablets are indicated for the symptomatic relief of sinusitis, bronchitis, pharyngitis, and coryza when these conditions are associated with nasal congestion and viscous mucus in the lower respiratory tract.


Adults and children 12 years of age and older: one tablet twice daily (every 12 hours).

Children 6 to under 12 years: one-half (1/2) tablet twice daily (every 12 hours). Phenylpropanolamine HCl w/guaifenesin long acting tablets are not recommended for children under 6 years of age.

Tablets may be broken in half for ease of administration without affecting release of medication but should not be crushed or chewed prior to swallowing.


Tablet, sustained release capsule(entex LA (guaifenesin and phenylephrine) ): Guaifenesin 600 mg and phenylephine HCL 30 mg

Side Effects & Drug Interactions


Possible adverse reactions include nervousness, insomnia, restlessness, headache, nausea, or gastric irritation. These reactions seldom, if ever, require discontinuation of therapy. Urinary retention may occur in patients with prostatic hypertrophy.

Side effects may include:
Anxiety, convulsions, depression, difficulty breathing, difficulty urinating (in men with an enlarged prostate), hallucinations, headache, inability to sleep or difficulty sleeping, increased heart beat, irritability, irritated stomach, nausea, nervousness, paleness, palpitations, restlessness, tremor, weakness, vomiting


Phenyephrine HCl w/guaifenesin long acting tablets should not be used in patients taking monoamine oxidase inhibitors or other sympathomimetics.

Do not take Entex LA (guaifenesin and phenylephrine) if you are taking a medication classified as an MAO inhibitor, including the antidepressants Nardil and Parnate. Avoid other stimulating drugs such as Proventil, Ventolin, and many decongestants. Interactions can also occur with the following:

Bromocriptine (Parlodel)
Mecamylamine (Inversine)
Methyldopa (Aldomet)
Reserpine (Diupres, Hydropres)

Warnings & Precautions


Sympathomimetic amines should be used with caution in patients with hypertension, diabetes mellitus, heart disease, peripheral vascular disease, increased intraocular pressure, hyperthyroidism, or prostatic hypertrophy.


Information for the Patient: Do not crush or chew phenylephrine HCl w/ guaifenesin long acting tablets prior to swallowing.

Drug/Laboratory Test Interactions: Guaifenesin has been reported to interfere with clinical laboratory determinations of urinary 5-hydroxyindole-acetic acid (5-HIAA) and urinary vanillylmandelic acid (VMA).

Pregnancy: Pregnancy Category C. Animal reproduction studies have not been conducted with phenylephrine HCl w/guaifenesin long acting tablets. It is also not known whether phenylephrine HCl w/guaifenesin long acting tablets, can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. Phenylephrine HCl w/guaifenesin long acting tablets, should be given to a pregnant woman only if clearly needed.

Nursing Mothers: It is not known whether the drugs in phenylephrine HCl w/guaifenesin long acting tablets, are excreted in human milk. Because many drugs are excreted in human milk and because of the potential for serious adverse reactions in nursing infants, a decision should be made whether to discontinue nursing or to discontinue the product, taking into account the importance of the drug to the mother.

Pediatric Use: Safety and effectiveness of phenylephrine HCl w/guaifenesin long acting tablets, in children below the age of 6 have not been established.

Overdose & Contraindications


The treatment of overdosage should provide symptomatic and supportive care. If the amount ingested is considered dangerous or excessive, induce vomiting with ipecac syrup unless the patient is convulsing, comatose, or has lost the gag reflex, in which case perform gastric lavage using a large-bore tube. If indicated, follow with activated charcoal and a saline cathartic. Since the effects of phenylephrine HCl w/guaifenesin long acting tablet may last up to 12 hours, treatment should be continued for at least that length of time.


Phenylephrine HCl w/guaifenesin long acting tablets are contraindicated in individuals with known hypersensitivity to sympathomimetics, severe hypertension, ventricular tachycardia, or in patients receiving monoamine oxidase inhibitors.

Clinical Pharmacology


Phenylephrine hydrochloride produces vasoconstriction that lasts longer than that of epinephrine and ephedrine. Responses are more sustained than those of epinephrine, lasting 20 minutes after intravenous and as long as 50 minutes after subcutaneous injection. Its action on the heart contrasts sharply with that of epinephrine and ephedrine, in that it slows the heart rate and increases the stroke output, producing no disturbance in the rhythm of the pulse.

Phenylephrine is a powerful postsynaptic alpha-receptor stimulant with little effect on the beta receptors of the heart. In therapeutic doses, it produces little if any stimulation of either the spinal cord or cerebrum. A singular advantage of this drug is the fact that repeated injections produce comparable effects.

The predominant actions of phenylephrine are on the cardiovascular system. Parenteral administration causes a rise in systolic and diastolic pressures in man and other species. Accompanying the pressor response to phenylephrine is a marked reflex bradycardia that can be blocked by atropine; after atropine, large doses of the drug increase the heart rate only slightly. In man, cardiac output is slightly decreased and peripheral resistance is considerably increased. Circulation time is slightly prolonged, and venous pressure is slightly increased; venous constriction is not marked. Most vascular beds are constricted; renal, splanchnic, cutaneous, and limb blood flows are reduced but coronary blood flow is increased. Pulmonary vessels are constricted, and pulmonary arterial pressure is raised.

The drug is a powerful vasoconstrictor, with properties very similar to those of norepinephrine but almost completely lacking the chronotropic and inotropic actions on the heart. Cardiac irregularities are seen only very rarely even with large doses.

Guaifenesin promotes lower respiratory tract drainage by thinning bronchial secretions, lubricates irritated respiratory tract membranes through increased mucous flow, and facilitates removal of viscous, inspissated mucus. As a result of these drugs, sinus and bronchial drainage is improved, and dry, nonproductive coughs become more productive and less frequent.

Medication Guide


Guaifenesin with phenylephrine is used for the symptomatic relief of a respiratory condition characterized by a stuffy nose, mucous in the respiratory tract, and dry, nonproductive cough caused by colds, flu, or hay fever. Inform your physician if you are pregnant or nursing. Inform your physician or pharmacist if you have high blood pressure, diabetes, glaucoma, heart disease, or an overactive thyroid. Do not take diet pills while taking this medication. Do not take this medication with a monoamine oxidase inhibitor. This medication may be taken with or without food. Drink a glass of water with each dose. Guaifenesin with phenylephrine may cause trouble sleeping; take your last dose of the day several hours before bedtime. Notify your physician if you develop trouble breathing or a fast, pounding or irregular heart beat. Notify your physician if your cough lasts for more than one week.

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