Fentuss Expectorant Side Effects
Generic name: guaifenesin / hydrocodone
Medically reviewed by Drugs.com. Last updated on Aug 20, 2022.
Note: This document contains side effect information about guaifenesin / hydrocodone. Some of the dosage forms listed on this page may not apply to the brand name Fentuss Expectorant.
For the Consumer
Oral route (Solution)
Warning: Addiction, Abuse, and Misuse; Life-Threatening Respiratory Depression, Accidental Ingestion, Medication Errors; Cytochrome P450 3A4 Interaction; Concomitant Use with Benzodiazepines or Other CNS Depressants; Interaction with Alcohol; Neonatal Opioid Withdrawal SyndromeHydrocodone bitartrate/guaifenesin exposes users to risks of addiction, abuse, and misuse, which can lead to overdose and death. Assess patient’s risk before prescribing and monitor closely for these behaviors and conditions.Serious, life-threatening, or fatal respiratory depression may occur. Monitor closely, especially upon initiation or when used in patients at higher risk.Accidental ingestion of hydrocodone bitartrate/guaifenesin, especially by children, can result in a fatal overdose of hydrocodoneEnsure accuracy when prescribing, dispensing, and administering hydrocodone bitartrate/guaifenesin. Dosing errors can result in accidental overdose and death.Concomitant use with CYP3A4 inhibitors (or discontinuation of CYP3A4 inducers) can result in a fatal overdose of hydrocodone. Avoid the use of hydrocodone bitartrate/guaifenesin in patients taking CYP3A4 inhibitors or inducers.Concomitant use of opioids with benzodiazepines or other central nervous system (CNS) depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death. Avoid use of hydrocodone bitartrate/guaifenesin in patients taking benzodiazepines, other CNS depressants, or alcohol.Instruct patients not to consume alcohol or any products containing alcohol while taking hydrocodone bitartrate/guaifenesin because co-ingestion can result in fatal plasma hydrocodone levels.Hydrocodone bitartrate/guaifenesin is not recommended for use in pregnant women. Prolonged use of hydrocodone bitartrate/guaifenesin during pregnancy can result in neonatal opioid withdrawal syndrome, which may be life-threatening if not recognized and treated. If hydrocodone bitartrate/guaifenesin is used for a prolonged period in a pregnant woman, advise the patient of the risk of neonatal opioid withdrawal syndrome and ensure that appropriate treatment will be available.
Oral route (Tablet)
Addiction, Abuse, and Misuse
Hydrocodone bitartrate and guaifenesin tablets exposes patients and other users to the risks of opioid addiction, abuse, and misuse, which can lead to overdose and death. Reserve hydrocodone bitartrate and guaifenesin tablets for use in adult patients for whom the benefits of cough suppression are expected to outweigh the risks, and in whom an adequate assessment of the etiology of the cough has been made. Assess each patient’s risk prior to prescribing hydrocodone bitartrate and guaifenesin tablets, prescribe hydrocodone bitartrate and guaifenesin tablets for the shortest duration that is consistent with individual patient treatment goals, monitor all patients regularly for the development of addition or abuse, and refill only after reevaluation of the need for continued treatment.
Life-Threatening Respiratory Depression
Serious, life-threatening, or fatal respiratory depression may occur with use of hydrocodone bitartrate and guaifenesin tablets. Monitor for respiratory depression, especially during initiation of hydrocodone bitartrate and guaifenesin tablets therapy or when used in patients at higher risk.
Accidental ingestion of even one dose of hydrocodone bitartrate and guaifenesin tablets, especially by children, can result in a fatal overdose of hydrocodone.Risk of Medication ErrorsEnsure accuracy when prescribing, dispensing, and administering hydrocodone bitartrate and guaifenesin tablets. Dosing errors can result in accidental overdose and death.Cytochrome P450 3A4 Interaction:The concomitant use of hydrocodone bitartrate and guaifenesin tablets with all cytochrome P450 3A4 inhibitors may result in an increase in hydrocodone plasma concentrations, which could increase or prolong adverse drug effects and may cause potentially fatal respiratory depression. In addition, discontinuation of a concomitantly used cytochrome P450 3A4 inducer may result in an increase in hydrocodone plasma concentration. Avoid the use of hydrocodone bitartrate and guaifenesin tablets in patients taking a CYP3A4 inhibitor or inducer.
Risks from Concomitant Use with Benzodiazepines or Other CNS Depressants
Concomitant use of opioids with benzodiazepines or other central nervous system (CNS) depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death. Avoid the use of hydrocodone bitartrate and guaifenesin tablets in patients taking benzodiazepines, other CNS depressants, or alcohol.Interaction with Alcohol:Instruct patients not to consume alcoholic beverages or use prescription or non-prescription products that contain alcohol while taking hydrocodone bitartrate and guaifenesin tablets. The co-ingestion of alcohol with hydrocodone bitartrate and guaifenesin tablets may result in increased plasma levels and a potentially fatal overdose of hydrocodone.
Neonatal Opioid Withdrawal Syndrome
Hydrocodone bitartrate and guaifenesin tablets is not recommended for use in pregnant women. Prolonged use of hydrocodone bitartrate and guaifenesin tablets during pregnancy can result in neonatal opioid withdrawal syndrome, which may be life-threatening if not recognized and treated, and requires management according to protocols developed by neonatology experts. If hydrocodone bitartrate and guaifenesin tablets is used for a prolonged period in a pregnant woman, advise the patient of the risk of neonatal opioid withdrawal syndrome and ensure that appropriate treatment will be available
Side effects requiring immediate medical attention
Along with its needed effects, guaifenesin / hydrocodone may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor immediately if any of the following side effects occur while taking guaifenesin / hydrocodone:
Incidence not known
- bladder pain
- bloating or swelling of the face, arms, hands, lower legs, or feet
- bloody or cloudy urine
- changes in vision
- darkening of the skin
- difficult, burning, or painful urination
- difficulty swallowing or breathing
- dizziness, faintness, or lightheadedness when getting up suddenly from lying or sitting position
- fast heartbeat
- frequent urge to urinate
- hives, itching, skin rash
- irregular, fast or slow, or shallow breathing
- loss of appetite
- loss of consciousness
- mental depression
- overactive reflexes
- pains in stomach, side, or abdomen, possibly radiating to the back
- pale or blue lips, fingernails, or skin
- poor coordination
- puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
- rapid weight gain
- restlessness shivering talking or acting with excitement you cannot control
- tightness in the chest
- tingling of the hands or feet
- trembling or shaking twitching
- unusual weight gain or loss
- yellow eyes or skin
Side effects not requiring immediate medical attention
Some side effects of guaifenesin / hydrocodone may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.
Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
- difficulty having a bowel movement
- feeling of warmth
- lack or loss of strength
- redness of the face, neck, arms, and occasionally, upper chest
- sleepiness or unusual drowsiness
- stomach pain
- sudden sweating
- trouble sleeping
For Healthcare Professionals
Applies to guaifenesin / hydrocodone: oral capsule, oral liquid, oral syrup, oral tablet, oral tablet extended release
The most commonly reported adverse effects have included headache, dizziness, sedation, nausea, diarrhea, decreased blood pressure, and flushing.[Ref]
Frequency not reported: Sedation (somnolence), headache, dizziness, decreased mental alertness with impaired mental and/or physical abilities
-Increased intracranial pressure[Ref]
Frequency not reported: Dose-related respiratory depression including fatal respiratory depression[Ref]
Frequency not reported: Nausea, diarrhea
Frequency not reported: Hot flush[Ref]
Frequency not reported: Decreased blood pressure[Ref]
More about Fentuss Expectorant (guaifenesin / hydrocodone)
Related treatment guides
1. Covington TR, eds., Lawson LC, Young LL "Handbook of Nonprescription Drugs." Washington, DC: American Pharmaceutical Association (1993):
2. "Product Information. Flowtuss (guaifenesin-hydrocodone)." Mission Pharmacal Company (2017):
3. Turturro MA, Paris PM, Yealy DM, Menegazzi JJ "Hydrocodone versus codeine in acute musculoskeletal pain." Ann Emerg Med 20 (1991): 1100-3
4. Morrow PL, Faris EC "Death associated with inadvertent hydrocodone overdose in a child with a respiratory tract infection." Am J Forensic Med Pathol 8 (1987): 60-3
5. Fricke J, Halladay SC, Bynum L, Francisco CA "Pain relief after dental impaction surgery using ketorolac, hydrocodone plus acetaminophen, or placebo." Clin Ther 15 (1993): 500-9
6. Sackner MA "Effects of hydrocodone bitartrate on breathing pattern of patients with chronic obstructive pulmonary disease and restrictive lung disease." Mt Sinai J Med 51 (1984): 222-6
7. "Product Information. Robitussin (guaifenesin)." Wyeth-Ayerst Laboratories (2001):
8. "Product Information. Vicodin Tuss (guaifenesin-hydrocodone)." Knoll Pharmaceutical Company (2001):
9. Sorensen JL, Hargreaves WA, Weinberg JA "Heroin addict responses to six weeks of detoxification with LAAM." Drug Alcohol Depend 9 (1982): 79-87
Some side effects may not be reported. You may report them to the FDA.