G-Vent Side Effects
Generic Name: guaifenesin / phenylpropanolamine
Note: This document contains side effect information about guaifenesin / phenylpropanolamine. Some of the dosage forms listed on this page may not apply to the brand name G-Vent.
Applies to guaifenesin/phenylpropanolamine: oral capsule extended release, oral liquid, oral tablet, oral tablet extended release
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]
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]
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 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 reactions to phenylpropanolamine may occur.[Ref]
Rarely, phenylpropanolamine may cause acute interstitial nephritis.[Ref]
Rash may rarely occur in patients taking guaifenesin.[Ref]
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. Bernstein E, Diskant BM "Phenylpropanolamine: a potentially hazardous drug." Ann Emerg Med 11 (1982): 311-5
4. 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
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. 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
7. McEwen J "Phenylpropanolamine-associated hypertension after the use of "over- the-counter" appetite-suppressant products." Med J Aust 2 (1983): 71-3
8. Chin C, Choy M "Cardiomyopathy induced by phenylpropanolamine." J Pediatr 123 (1993): 825-7
9. 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
10. 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
11. Howrie DL, Wolfson JH "Phenylpropanolamine-induced hypertensive seizures." J Pediatr 102 (1983): 143-5
12. Mueller SM "Neurologic complications of phenylpropanolamine use." Neurology 33 (1983): 650-2
13. 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
14. Pentel PR, Mikell FL, Zavoral JH "Myocardial injury after phenylpropanolamine ingestion." Br Heart J 47 (1982): 51-4
15. Clark JE, Simon WA "Cardiac arrhythmias after phenylpropanolamine ingestion." Drug Intell Clin Pharm 17 (1983): 737-8
16. Norvenius G, Widerlov E, Lonnerholm G "Phenylpropanolamine and mental disturbances" Lancet 2 (1979): 1367-8
17. Johnson DA, Etter HS, Reeves DM "Stroke and phenylpropanolamine use" Lancet 2 (1983): 970
18. 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
19. Schaffer CB, Pauli MW "Psychotic reaction caused by proprietary oral diet agents." Am J Psychiatry 137 (1980): 1256-7
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. Achor MB, Extein I "Diet aids, mania, and affective illness" Am J Psychiatry 138 (1981): 392
25. Elliott CF, Whyte JC "Phenylpropanolamine and hypertension." Med J Aust 1 (1981): 715
26. Kikta DG, Devereaux MW, Chandar K "Intracranial hemorrhages due to phenylpropanolamine." Stroke 16 (1985): 510-2
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. Kase CS, Foster TE, Reed JE, Spatz EL, Girgis GN "Intracerebral hemorrhage and phenylpropanolamine use." Neurology 37 (1987): 399-404
30. Kizer KW "Intracranial hemorrhage associated with overdose of decongestant containing phenylpropanolamine" Am J Emerg Med 2 (1984): 180-1
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
Some side effects may not be reported. You may report them to the FDA.