Drug Interactions between G-Tusicof and metipranolol ophthalmic
This report displays the potential drug interactions for the following 2 drugs:
- G-Tusicof (dextromethorphan/guaifenesin/phenylephrine)
- metipranolol ophthalmic
Interactions between your drugs
metipranolol ophthalmic phenylephrine
Applies to: metipranolol ophthalmic and G-Tusicof (dextromethorphan / guaifenesin / phenylephrine)
MONITOR: A case report suggests that beta-blockers may enhance the pressor response to phenylephrine. The proposed mechanism involves blockade of beta-2 adrenergic receptors in the peripheral vasculature, resulting in unopposed alpha-adrenergic effect of phenylephrine that is responsible for vasoconstriction. Additionally, beta-blockers may desensitize baroreceptors that normally modulate heart rate in response to blood pressure elevations by increasing vagal activity on the sinoauricular node. In the case report, a woman with a history of hypertension treated with hydrochlorothiazide (50 mg twice a day) and propranolol (40 mg four times a day) developed sudden bitemporal pain and became unconscious shortly after she was given one drop of a 10% phenylephrine solution in each eye during an ophthalmic examination. She subsequently died of intracerebral hemorrhage due to rupture of a berry aneurysm. The authors noted that the patient had received the same eye drop without incident on two previous occasions when she was not receiving blood pressure or other medications. Nevertheless, an interaction between phenylephrine and beta-blockers is not well established. Phenylephrine acts predominantly on alpha-adrenergic receptors and has little or no direct effect on beta-2 adrenergic receptors, although it may affect them indirectly by enhancing release of norepinephrine from adrenergic nerve terminals. In a study of 12 patients with hypertension, mean phenylephrine doses required to increase systolic blood pressure by 25 mmHg were not significantly different following 2 weeks on propranolol, metoprolol, and placebo (4.8 mcg/kg, 4.7 mcg/kg, and 5.3 mcg/kg, respectively). Baroreceptor-mediated decreases in heart rate during phenylephrine infusion were also in the same range on propranolol, metoprolol, and placebo over baseline heart rate values. In another study, no changes in blood pressure or heart rate were observed in hypertensive patients treated with metoprolol who were given 0.5 to 4 mg doses of phenylephrine intranasally every hour up to a total of 7.5 to 15 mg, or 4 to 30 times the usual recommended dose, compared to placebo or baseline values. These results support the lack of a significant interaction between beta-blockers and phenylephrine.
MANAGEMENT: Until more information is available, caution should be exercised when phenylephrine is used in combination with beta-blockers including ophthalmic formulations, which may be systemically absorbed and can produce clinically significant systemic effects even at low or undetectable plasma levels. Monitoring of blood pressure should be considered, particularly when phenylephrine is administered intravenously or intraocularly. Although an interaction is not likely to occur with cardioselective beta-blockers, caution may be advisable when high dosages are used, since cardioselectivity is not absolute and may be lost with larger doses. A beta-blocker such as propranolol may be used to treat cardiac arrhythmias that occur during administration of phenylephrine.
References
- Cass E, Kadar D, Stein HA (1979) "Hazards of phenylephrine topical medication in persons taking propranolol." Can Med Assoc J, 120, p. 1261-2
- Myers MG, Iazzetta JJ (1982) "Intranasally administered phenylephrine and blood pressure." Can Med Assoc J, 127, p. 365-6
Drug and food interactions
dextromethorphan food
Applies to: G-Tusicof (dextromethorphan / guaifenesin / phenylephrine)
GENERALLY AVOID: Alcohol may potentiate some of the pharmacologic effects of CNS-active agents. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills.
MANAGEMENT: Patients receiving CNS-active agents should be warned of this interaction and advised to avoid or limit consumption of alcohol. Ambulatory patients should be counseled to avoid hazardous activities requiring complete mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.
References
- Warrington SJ, Ankier SI, Turner P (1986) "Evaluation of possible interactions between ethanol and trazodone or amitriptyline." Neuropsychobiology, 15, p. 31-7
- Gilman AG, eds., Nies AS, Rall TW, Taylor P (1990) "Goodman and Gilman's the Pharmacological Basis of Therapeutics." New York, NY: Pergamon Press Inc.
- (2012) "Product Information. Fycompa (perampanel)." Eisai Inc
- (2015) "Product Information. Rexulti (brexpiprazole)." Otsuka American Pharmaceuticals Inc
phenylephrine food
Applies to: G-Tusicof (dextromethorphan / guaifenesin / phenylephrine)
MONITOR: Coadministration of two or more sympathomimetic agents may increase the risk of adverse effects such as nervousness, irritability, and increased heart rate. Central nervous system (CNS) stimulants, particularly amphetamines, can potentiate the adrenergic response to vasopressors and other sympathomimetic agents. Additive increases in blood pressure and heart rate may occur due to enhanced peripheral sympathetic activity.
MANAGEMENT: Caution is advised if two or more sympathomimetic agents are coadministered. Pulse and blood pressure should be closely monitored.
References
- Rosenblatt JE, Lake CR, van Kammen DP, Ziegler MG, Bunney WE Jr (1979) "Interactions of amphetamine, pimozide, and lithium on plasma norepineophrine and dopamine-beta-hydroxylase in schizophrenic patients." Psychiatry Res, 1, p. 45-52
- Cavanaugh JH, Griffith JD, Oates JA (1970) "Effect of amphetamine on the pressor response to tyramine: formation of p-hydroxynorephedrine from amphetamine in man." Clin Pharmacol Ther, 11, p. 656
- (2001) "Product Information. Adderall (amphetamine-dextroamphetamine)." Shire Richwood Pharmaceutical Company Inc
- (2001) "Product Information. Tenuate (diethylpropion)." Aventis Pharmaceuticals
- (2001) "Product Information. Sanorex (mazindol)." Novartis Pharmaceuticals
- (2001) "Product Information. Focalin (dexmethylphenidate)." Mikart Inc
- (2002) "Product Information. Strattera (atomoxetine)." Lilly, Eli and Company
Therapeutic duplication warnings
No warnings were found for your selected drugs.
Therapeutic duplication warnings are only returned when drugs within the same group exceed the recommended therapeutic duplication maximum.
See also
Drug Interaction Classification
Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit. | |
Moderately clinically significant. Usually avoid combinations; use it only under special circumstances. | |
Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan. | |
No interaction information available. |
Further information
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