Entex HC Side Effects
Generic name: guaifenesin / hydrocodone / pseudoephedrine
Medically reviewed by Drugs.com. Last updated on Oct 25, 2022.
Note: This document contains side effect information about guaifenesin / hydrocodone / pseudoephedrine. Some dosage forms listed on this page may not apply to the brand name Entex HC.
Applies to guaifenesin / hydrocodone / pseudoephedrine: oral solution.
- This drug may be habit-forming with long-term use.
- This drug has an opioid drug in it. Opioid drugs can put you at risk for addiction, abuse, and misuse. Misuse or abuse of this drug can lead to overdose and death. If you have questions, talk with your doctor.
- This drug has an opioid drug in it. Severe side effects have happened when opioid drugs were used with benzodiazepines or other drugs that may make you drowsy or slow your actions. This includes slow or troubled breathing and death. Benzodiazepines include drugs like alprazolam, diazepam, and lorazepam. Benzodiazepines may be used to treat many health problems like anxiety, trouble sleeping, or seizures. If you have questions, talk with your doctor.
- Many drugs interact with this drug and can raise the chance of side effects like deadly breathing problems. Talk with your doctor and pharmacist to make sure it is safe to use this drug with all of your drugs.
- Do not take with alcohol or products that have alcohol. Unsafe and sometimes deadly effects may happen.
- Get medical help right away if you feel very sleepy, very dizzy, or if you pass out. Caregivers or others need to get medical help right away if the patient does not respond, does not answer or react like normal, or will not wake up.
- Very bad and sometimes deadly breathing problems have happened with this drug. Talk with the doctor.
- Get medical help right away if you have slow breathing, shallow breathing, or trouble breathing.
- Even one dose of this drug may be deadly if it is taken by someone else or by accident, especially in children. If this drug is taken by someone else or by accident, get medical help right away.
- Keep all drugs in a safe place. Keep all drugs out of the reach of children and pets.
- Do not take if you are pregnant.
- Using this drug for a long time during pregnancy may lead to withdrawal in the newborn baby. This can be life-threatening. Talk with the doctor.
- Be sure that you know your dose and how to take this drug. Dosing errors can lead to accidental overdose and death. If you have any questions, talk with your doctor or pharmacist.
Serious side effects of Entex HC
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.
- Signs of high or low blood pressure like very bad headache or dizziness, passing out, or change in eyesight.
- Chest pain or pressure or a fast heartbeat.
- Trouble breathing, slow breathing, or shallow breathing.
- Feeling confused.
- A heartbeat that does not feel normal.
- Hallucinations (seeing or hearing things that are not there).
- Mood changes.
- Very bad belly pain.
- Trouble passing urine.
- Change in eyesight.
- Very upset stomach or throwing up.
- Very bad constipation.
- Feeling very tired or weak.
- Feeling very sleepy.
- Taking an opioid drug like this drug may lead to a rare but very bad adrenal gland problem. Call your doctor right away if you have very bad dizziness or passing out, very bad upset stomach or throwing up, or if you feel less hungry, very tired, or very weak.
- A severe and sometimes deadly problem called serotonin syndrome may happen if you take this drug with certain other drugs. Call your doctor right away if you have agitation; change in balance; confusion; hallucinations; fever; fast or abnormal heartbeat; flushing; muscle twitching or stiffness; seizures; shivering or shaking; sweating a lot; severe diarrhea, upset stomach, or throwing up; or severe headache.
Other side effects of Entex HC
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:
- Feeling nervous and excitable.
- Not able to sleep.
- Feeling sleepy.
- Upset stomach or throwing up.
- Sweating a lot.
- Feeling tired or weak.
- Dry mouth.
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 1-800-332-1088. You may also report side effects at https://www.fda.gov/medwatch.
For Healthcare Professionals
The most common adverse events were sedation (somnolence, mental clouding, lethargy), impaired mental and physical performance, lightheadedness, dizziness, headache, dry mouth, nausea, vomiting, constipation, tachycardia, arrhythmias including premature ventricular contractions, CNS stimulation including anxiety, restlessness, nervousness, tremor, and irritability.[Ref]
Frequency not reported: Increased blood pressure, decreased blood pressure, tachycardia, chest pain, orthostatic hypotension, palpitations, syncope, prolonged QT interval, hot flush, atrial fibrillation, myocardial infarction, arrhythmias including premature ventricular contractions, flushing
Frequency not reported: Confusion, anxiety, dysphoria, agitation, addiction, abuse, misuse, fear, depression, hyperactivity, ataxia, hallucinations, hyperexcitability, opioid withdrawal syndrome, drug abuse, drug dependence
Serotonin syndrome has been reported with concomitant opioids and serotonergic drugs.
Frequency not reported: Coma, ataxia, somnolence, facial dyskinesia, tremor, insomnia, migraine, increased intracranial pressure, seizure, dizziness, impaired mental and physical performance, serotonin syndrome
Frequency not reported: Abdominal pain, bowel obstruction, diarrhea, difficulty swallowing, GERD, indigestion, pancreatitis, paralytic ileus, dysgeusia, ischemic colitis, increase of serum amylase, dry mouth, biliary tract spasm (spasm of the sphincter of Oddi)
Frequency not reported: Adrenal insufficiency, androgen deficiency
Adrenal insufficiency has been reported with opioid use, most often following greater than one month of use. Androgen deficiency has been reported with chronic opioid use.
Frequency not reported: Miosis, visual disturbances
Frequency not reported: Decreased appetite
More about Entex HC (guaifenesin / hydrocodone / pseudoephedrine)
- Check interactions
- Dosage information
- During pregnancy
- Drug class: upper respiratory combinations
- En español
Related treatment guides
1. "Product Information. Hycofenix (guaifenesin / hydrocodone / pseudoephedrine)." Mission Pharmacal Company (2017):
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.