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Gentex HC Side Effects

Generic Name: guaifenesin / hydrocodone / phenylephrine

Note: This document contains side effect information about guaifenesin / hydrocodone / phenylephrine. Some of the dosage forms listed on this page may not apply to the brand name Gentex HC.

Applies to guaifenesin / hydrocodone / phenylephrine: oral elixir, oral liquid, oral syrup

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Like other narcotic medications, hydrocodone can slow your breathing. Death may occur if breathing becomes too weak.

A person caring for you should seek emergency medical attention if you have slow breathing with long pauses, blue colored lips, or if you are hard to wake up.

Stop using this medicine and call your doctor at once if you have:

  • severe dizziness or drowsiness;

  • noisy breathing, sighing, shallow breathing;

  • severe restlessness or nervousness;

  • severe constipation;

  • pounding heartbeats or fluttering in your chest; or

  • painful or difficult urination.

Serious side effects may be more likely in older adults and those who are overweight, malnourished, or debilitated.

Common side effects may include:

  • mild drowsiness;

  • dryness of your eyes, nose, and mouth;

  • blurred vision; or

  • nausea, vomiting, diarrhea, constipation.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects.

Further information

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

Some side effects may not be reported. You may report them to the FDA.

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