G-Vent Side Effects

Generic Name: guaifenesin / phenylpropanolamine

Note: This page contains information about the side effects of guaifenesin / phenylpropanolamine. Some of the dosage forms included on this document may not apply to the brand name G-Vent.

Not all side effects for G-Vent may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

For the Consumer

Applies to guaifenesin / phenylpropanolamine: oral capsule extended release, oral liquid, oral tablet, oral tablet extended release

No serious side effects from guaifenesin and phenylpropanolamine are expected. Seek emergency medical attention if you experience an allergic reaction (difficulty breathing; closing of your throat; swelling of your lips, tongue, or face; or hives).

Other, less serious side effects may be more likely to occur. Continue to take guaifenesin and phenylpropanolamine and talk to your doctor if you experience

  • dizziness or headache;

  • nervousness, restlessness, or insomnia;

  • nausea or stomach upset; or

  • difficulty urinating.

Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome.

For Healthcare Professionals

Applies to guaifenesin / phenylpropanolamine: oral capsule extended release, oral liquid, oral tablet, oral tablet extended release

Cardiovascular

Cardiovascular adverse effects may be associated with the use of phenylpropanolamine. Phenylpropanolamine can cause a significant rise in heart rate. Hypertension and arrhythmias may be problematic in susceptible patients. Cardiovascular side effects have also included an increased risk of hemorrhagic stroke.[Ref]

Phenylpropanolamine causes vasoconstriction which usually does not result in blood pressure elevations in healthy adults given normally prescribed dosages. However, phenylpropanolamine administration may be problematic for patients with preexisting hypertension and those receiving higher dosages. In general, 75-mg of sustained-release phenylpropanolamine will not produce a significant increase in blood pressure in normotensive patients, but 150-mg of sustained-release phenylpropanolamine can.

The combination of caffeine and phenylpropanolamine is more apt to cause hypertension. Although caffeine is no longer added to phenylpropanolamine as an anorexiant, this combination is available as "look-alikes" for amphetamines. Hypertensive crisis has occurred occasionally subsequent to overuse, overdose, and ingestion of normally recommended doses. Hypertensive crisis may be accompanied by headache, blurred vision, confusion, intracranial hemorrhage, encephalopathy, or seizures.

Arrhythmias may be produced in predisposed patients. The majority of reports of arrhythmias involve overuse or overdose. Rarely, high doses of phenylpropanolamine may cause chest pain and evidence of myocardial injury.

One study reported that taking phenylpropanolamine increases the risk of hemorrhagic stroke in women. Men may also be at risk. Although the risk of hemorrhagic stoke is very low, the FDA recommends that all use of phenylpropanolamine be discontinued.[Ref]

Nervous system

Phenylpropanolamine produces nervous system stimulation, resulting in tremor, anxiety, insomnia, dizziness, and nervousness. Headache may also occur. Guaifenesin may rarely cause dizziness and headache.[Ref]

Seizures may occur in rare cases of hypertensive crisis due to phenylpropanolamine and have been reported with normally recommended doses as well as in cases of overuse or overdose.

There have been anecdotal reports of cerebrovascular hemorrhage largely associated with an uneven pattern of cerebrovascular spasm referred to as vascular beading. Vascular beading has also been reported in the absence of hemorrhage. Intracranial hemorrhage has almost always been associated with hypertension.[Ref]

Psychiatric

Psychotic reactions to phenylpropanolamine have occurred in patients receiving normally recommended doses and in cases of abuse. In a few patients phenylpropanolamine appears to have exacerbated an underlying bipolar disorder which was previously undiagnosed.

A psychotic episode consisting of abnormal behavior was reported in a young woman following a week of therapy with Naldecon (phenylephrine, phenylpropanolamine, chlorpheniramine, and phenyltoloxamine) and amantadine. The patient had no personal or family history of psychiatric illness and no history of recreational substance use. It is uncertain whether the episode was due to the amantadine, the phenylpropanolamine or another component in the Naldecon, or an interaction between the drugs.[Ref]

Psychiatric reactions to phenylpropanolamine occur infrequently but include acute mania, anxiety, paranoia, confusion, agitation, and hallucinations. These reactions may be more common in women.[Ref]

Gastrointestinal

Gastrointestinal complaints most commonly reported with phenylpropanolamine are anorexia and gastric irritation. Nausea and vomiting have occurred in conjunction with hypertensive episodes. Guaifenesin may cause gastrointestinal upset and vomiting, most often with higher than recommended doses.[Ref]

Hypersensitivity

Hypersensitivity reactions to phenylpropanolamine may occur.[Ref]

Renal

Rarely, phenylpropanolamine may cause acute interstitial nephritis.[Ref]

Dermatologic

Rash may rarely occur in patients taking guaifenesin.[Ref]

References

1. Noble R "A controlled clinical trial of the cardiovascular and psychological effects of phenylpropanolamine and caffeine." Drug Intell Clin Pharm 22 (1988): 296-9

2. Lake CR, Zaloga G, Clymer R, Quirk RM, Chernow B "A double dose of phenylpropanolamine causes transient hypertension." Am J Med 85 (1988): 339-43

3. O'Connell MB, Gross CR "The effect of multiple doses of phenylpropanolamine on the blood pressure of patients whose hypertension was controlled with beta blockers." Pharmacotherapy 11 (1991): 376-81

4. Bernstein E, Diskant BM "Phenylpropanolamine: a potentially hazardous drug." Ann Emerg Med 11 (1982): 311-5

5. Horowitz JD, Lang WJ, Howes LG, Fennessy MR, Christophidis N, Rand MJ, Louis WJ "Hypertensive responses induced by phenylpropanolamine in anorectic and decongestant preparations." Lancet 1 (1980): 60-1

6. O'Connell MB, Gross CR "The effect of single-dose phenylpropanolamine on blood pressure in patients with hypertension controlled by beta blockers." Pharmacotherapy 10 (1990): 85-91

7. Pentel PR, Mikell FL, Zavoral JH "Myocardial injury after phenylpropanolamine ingestion." Br Heart J 47 (1982): 51-4

8. Lake CR, Zaloga G, Bray J, Rosenberg D, Chernow B "Transient hypertension after two phenylpropanolamine diet aids and the effects of caffeine: a placebo-controlled follow-up study." Am J Med 86 (1989): 427-32

9. Kroenke K, Omori DM, Simmons JO, Wood DR, Meier NJ "The safety of phenylpropanolamine in patients with stable hypertension." Ann Intern Med 111 (1989): 1043-4

10. Clark JE, Simon WA "Cardiac arrhythmias after phenylpropanolamine ingestion." Drug Intell Clin Pharm 17 (1983): 737-8

11. Chin C, Choy M "Cardiomyopathy induced by phenylpropanolamine." J Pediatr 123 (1993): 825-7

12. McEwen J "Phenylpropanolamine-associated hypertension after the use of "over- the-counter" appetite-suppressant products." Med J Aust 2 (1983): 71-3

13. Howrie DL, Wolfson JH "Phenylpropanolamine-induced hypertensive seizures." J Pediatr 102 (1983): 143-5

14. Mueller SM "Neurologic complications of phenylpropanolamine use." Neurology 33 (1983): 650-2

15. Lake CR, Gallant S, Masson E, Miller P "Adverse drug effects attributed to phenylpropanolamine: a review of 142 case reports." Am J Med 89 (1990): 195-208

16. Norvenius G, Widerlov E, Lonnerholm G "Phenylpropanolamine and mental disturbances" Lancet 2 (1979): 1367-8

17. Lake CR, Tenglin R, Chernow B, Holloway HC "Psychomotor stimulant-induced mania in a genetically predisposed patient: a review of the literature and report of a case." J Clin Psychopharmacol 3 (1983): 97-100

18. Schaffer CB, Pauli MW "Psychotic reaction caused by proprietary oral diet agents." Am J Psychiatry 137 (1980): 1256-7

19. Johnson DA, Etter HS, Reeves DM "Stroke and phenylpropanolamine use" Lancet 2 (1983): 970

20. Cornelius JR, Soloff PH, Reynolds CF, 3d "Paranoia, homicidal behavior, and seizures associated with phenylpropanolamine." Am J Psychiatry 141 (1984): 120-1

21. "Product Information. Robitussin (guaifenesin)." Wyeth-Ayerst Laboratories, Philadelphia, PA.

22. Grieger TA, Clayton AH, Goyer PF "Affective disorder following use of phenylpropanolamine" Am J Psychiatry 147 (1990): 367-8

23. Maher LM, Peterson PL, Dela-Cruz C "Postpartum intracranial hemorrhage and phenylpropanolamine use" Neurology 37 (1987): 1686

24. Kizer KW "Intracranial hemorrhage associated with overdose of decongestant containing phenylpropanolamine" Am J Emerg Med 2 (1984): 180-1

25. Achor MB, Extein I "Diet aids, mania, and affective illness" Am J Psychiatry 138 (1981): 392

26. Elliott CF, Whyte JC "Phenylpropanolamine and hypertension." Med J Aust 1 (1981): 715

27. Edwards M, Russo L, Harwood-Nuss A "Cerebral infarction with a single oral dose of phenylpropanolamine." Am J Emerg Med 5 (1987): 163-4

28. Dietz AJ, Jr "Amphetamine-like reactions to phenylpropanolamine." JAMA 245 (1981): 601-2

29. Kikta DG, Devereaux MW, Chandar K "Intracranial hemorrhages due to phenylpropanolamine." Stroke 16 (1985): 510-2

30. Kase CS, Foster TE, Reed JE, Spatz EL, Girgis GN "Intracerebral hemorrhage and phenylpropanolamine use." Neurology 37 (1987): 399-404

31. Stroe AE, Hall J, Amin F "Psychotic episode related to phenylpropanolamine and amantadine in a healthy female." Gen Hosp Psychiatry 17 (1995): 457-8

32. Covington TR, Lawson LC, Young LL, eds. "Handbook of Nonprescription Drugs. 10th ed." Washington, DC: American Pharmaceutical Association (1993):

33. Speer F, Carrasco LC, Kimura CC "Allergy to phenylpropanolamine." Ann Allergy 40 (1978): 32-4

34. Swenson RD, Golper TA, Bennett WM "Acute renal failure and rhabdomyolysis after ingestion of phenylpropanolamine-containing diet pills." JAMA 248 (1982): 1216

35. Singer DR, Simpson JG, Catto GR, Johnston AW "Drug hypersensitivity causing granulomatous interstitial nephritis." Am J Kidney Dis 11 (1988): 357-9

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