Skip to Content

Histex-AC Side Effects

Generic Name: codeine / phenylephrine / triprolidine

Note: This document contains side effect information about codeine / phenylephrine / triprolidine. Some of the dosage forms listed on this page may not apply to the brand name Histex-AC.

For the Consumer

Applies to codeine / phenylephrine / triprolidine: oral syrup

What are some side effects that I need to call my doctor about right away?

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

  • Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
  • Very bad dizziness or passing out.
  • Chest pain or pressure or a fast heartbeat.
  • Trouble breathing, slow breathing, or shallow breathing.
  • Noisy breathing.
  • Feeling very sleepy.
  • Feeling confused.
  • A heartbeat that does not feel normal.
  • Hallucinations (seeing or hearing things that are not there).
  • Mood changes.
  • Seizures.
  • Very bad belly pain.
  • Very bad headache.
  • Trouble passing urine.
  • Shakiness.
  • Change in eyesight.
  • Very upset stomach or throwing up.
  • Very hard stools (constipation).
  • Feeling very tired or weak.

What are some other side effects of this drug?

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:

  • Dizziness.
  • Feeling nervous and excitable.
  • Not able to sleep.
  • Feeling sleepy.
  • Hard stools (constipation).
  • Upset stomach or throwing up.
  • Sweating a lot.
  • Feeling tired or weak.

These are not all of the side effects that may occur. If you have questions about side effects, call your doctor. Call your doctor for medical advice about side effects.

You may report side effects to the FDA at 1-800-FDA-1088. You may also report side effects at

For Healthcare Professionals

Applies to codeine/phenylephrine/triprolidine: oral liquid


The most commonly occurring side effects include dry mouth, dizziness, sleepiness, and disturbed coordination.[Ref]


Frequency not reported: Hypotension, palpitations, tachycardia, extrasystoles


Frequency not reported: Dry mouth, dry throat, epigastric distress, anorexia, nausea, vomiting, diarrhea, constipation


Frequency not reported: Urinary frequency, difficult urination, urinary retention


Frequency not reported: Confusion, restlessness, excitation, anxiety, nervousness, irritability, insomnia, euphoria, hysteria, hallucination


Frequency not reported: Blurred vision, diplopia


Frequency not reported: Chills, fatigue, vertigo, tinnitus


Frequency not reported: Drug rash, photosensitivity, excessive perspiration, urticaria

Nervous system

Frequency not reported: Sedation, sleepiness, dizziness, disturbed coordination, tremor, paresthesias, neuritis, convulsions, CNS depression


Frequency not reported: Nasal dryness, thickening of bronchial secretions, tightness of chest and wheezing, nasal stuffiness, respiratory depression


1. "American Geriatrics Society 2015 Updated Beers Criteria for Potentially Inappropriate Medication Use in Older Adults." J Am Geriatr Soc 63 (2015): 2227-46

2. "Product Information. Histex-AC (codeine / phenylephrine / triprolidine)." Allegis Pharmaceuticals, Canton, MS.

Some side effects of Histex-AC may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.