Interactions between Elranatamab and GDP-EX
1 drug interaction and 13 additional warnings found for the following 2 drugs:
- elranatamab
- GDP-EX (dextromethorphan/guaifenesin/phenylephrine)
Drug interactions
Moderate drug interactions
Moderate:
dextromethorphan elranatamab
Applies to: GDP-EX (dextromethorphan / guaifenesin / phenylephrine) and elranatamab
Monitor
Coadministration with elranatamab may increase the plasma concentrations of drugs that are substrates of CYP450 isoenzymes. Initiation of elranatamab treatment causes transient release of cytokines that may suppress CYP450 isoenzymes, although the potential for interaction has not been studied. According to the manufacturer, increased exposure to CYP450 substrate(s) is more likely after the first dose of elranatamab on day 1, and up to 14 days after the 32 mg dose on day 4, as well as during and after cytokine release syndrome (CRS).
Management
Caution is advised when elranatamab is administered with drugs that are metabolized by CYP450 isoenzymes, particularly those with a narrow therapeutic index, and sensitive substrates where minimal changes to concentration may lead to significant adverse reactions (e.g., carbamazepine, colchicine, cyclosporine, disopyramide, phenytoin, quinidine, theophylline, warfarin, macrolide immunosuppressants, vinca alkaloids, and some narcotic analgesics). Clinical and/or laboratory monitoring is recommended following elranatamab initiation and/or step-up doses, as well as during and after CRS. Individual product labeling for the CYP450 substrate(s) should be consulted for specific dosage adjustment recommendations.
References (6)
- (2025) "Product Information. Elrexfio (elranatamab)." Pfizer Australia Pty Ltd, pfpelrei10925
- (2025) "Product Information. ELREXFIO (elranatamabe)." PFIZER BRASIL LTDA
- (2026) "Product Information. Elrexfio (elranatamab)." Pfizer Ltd
- (2026) "Product Information. Elrexfio (elranatamab)." Pfizer Labs
- (2026) "Product Information. Elrexfio (elranatamab)." Pfizer Canada ULC
- (2025) "Product Information. ELREXFIO (elranatamab)." PFIZER EUROPE MA EEIG
Food/lifestyle interactions
Moderate food/lifestyle interactions
Moderate:
dextromethorphan Food/Lifestyle
Applies to: GDP-EX (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 (4)
- 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 America Pharmaceutical, Inc.
Moderate:
phenylephrine Caffeine
Applies to: GDP-EX (dextromethorphan / guaifenesin / phenylephrine)
Monitor
Coadministration of two or more sympathomimetic or noradrenergic agents may increase the risk of nervousness, irritability, tachycardia, and/or increased blood pressure. Central nervous system (CNS) stimulants, particularly amphetamines, can potentiate the adrenergic response to vasopressors and other sympathomimetic and/or noradrenergic agents, including norepinephrine transporter inhibitors. 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 or noradrenergic agents are coadministered. Pulse and blood pressure should be closely monitored. Consultation with individual product labeling, as well as relevant institutional protocols, may be advisable for further guidance.
References (20)
- 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
- (2024) "Product Information. Ephedrine (ephedrine)." Hameln Pharma Ltd
- (2023) "Product Information. Ephedrine Hydrochloride (ephedrine)." Wockhardt UK Ltd
- (2026) "Product Information. Strattera (atomoxetine)." Lilly, Eli and Company
- (2025) "Product Information. Atomoxetine (atomoxetine)." Zentiva Pharma UK Ltd
- (2026) "Product Information. Atomoxetine (Apo) (atomoxetine)." Arrotex Pharmaceuticals Pty Ltd
- Angita Pharma, Inc (2026) AG-ATOMOXETINE Product Monograph (Health Canada) https://pdf.hres.ca/dpd_pm/00059014.PDF
- (2026) "Product Information. Boots Decongestant (Pseudoephedrine) (pseudoephedrine)." The Boots Company Plc
- (2023) "Product Information. Sinus and Nasal Decongestant (Trust) (pseudoephedrine)." Noumed Pharmaceuticals Pty Ltd
- (2019) "Product Information. Ephedrine (ephedrine)." Pfizer Australia Pty Ltd
- (2024) "Product Information. EPHEDrine Sulfate (ePHEDrine)." Amneal Pharmaceuticals LLC
- (2024) "Product Information. Lemsip Cough Max for Mucus Cough and Cold (guaifenesin/paracetamol/phenylephrine)." Reckitt Benckiser Healthcare (UK) Ltd
- emc (2026) Product information: sudafed plus blocked nose 1mg/50mg/ml nasal spray. https://www.medicines.org.uk/emc/product/14256/smpc?utm_source=chatgpt.com
- (2023) "Product Information. EPHEDrine Sulfate (ePHEDrine)." Baxter Corporation
- Neo Health (OTC) Pty Ltd (2026) Product information: pseudoephedrine hydrochloride-paracetamol capsules. https://www.ebs.tga.gov.au/ebs/picmi/picmirepository.nsf/pdf?OpenAgent&id=CP-2024-PI-02603-1&d=20260804172310101&d=20260827172310101
Disease interactions
11 potential interactions Applies to: 11 conditions, including Benign Prostatic Hyperplasia, Hyperthyroidism, Diabetes Mellitus, Liver Disease, and Infection.
Benign Prostatic Hyperplasia
Moderate:
GDP-EX
The phenylephrine in GDP-EX has a moderate potential interaction with Benign Prostatic Hyperplasia.
Sympathomimetic agents may cause or worsen urinary difficulty in patients with prostate enlargement due to smooth muscle contraction in the bladder neck via stimulation of alpha-1 adrenergic receptors. Therapy with sympathomimetic agents should be administered cautiously in patients with hypertrophy or neoplasm of the prostate.
Cardiovascular Conditions and Disorders
Major:
GDP-EX
The phenylephrine in GDP-EX has a major potential interaction with Cardiovascular Conditions and Disorders.
Sympathomimetic agents may cause adverse cardiovascular effects, particularly when used in high dosages and/or in susceptible patients. In cardiac tissues, these agents may produce positive chronotropic and inotropic effects via stimulation of beta- 1 adrenergic receptors. Cardiac output, oxygen consumption, and the work of the heart may be increased. In the peripheral vasculature, vasoconstriction may occur via stimulation of alpha-1 adrenergic receptors. Palpitations, tachycardia, arrhythmia, hypertension, reflex bradycardia, coronary occlusion, cerebral vasculitis, myocardial infarction, cardiac arrest, and death have been reported. Some of these agents, particularly ephedra alkaloids (ephedrine, ma huang, phenylpropanolamine), may also predispose patients to hemorrhagic and ischemic stroke. Therapy with sympathomimetic agents should generally be avoided or administered cautiously in patients with sensitivity to sympathomimetic amines, hyperthyroidism, or underlying cardiovascular or cerebrovascular disorders. These agents should not be used in patients with severe coronary artery disease or severe/uncontrolled hypertension.
Cerebrovascular Insufficiency
Major:
GDP-EX
The phenylephrine in GDP-EX has a major potential interaction with Cerebrovascular Insufficiency.
Sympathomimetic agents may cause adverse cardiovascular effects, particularly when used in high dosages and/or in susceptible patients. In cardiac tissues, these agents may produce positive chronotropic and inotropic effects via stimulation of beta- 1 adrenergic receptors. Cardiac output, oxygen consumption, and the work of the heart may be increased. In the peripheral vasculature, vasoconstriction may occur via stimulation of alpha-1 adrenergic receptors. Palpitations, tachycardia, arrhythmia, hypertension, reflex bradycardia, coronary occlusion, cerebral vasculitis, myocardial infarction, cardiac arrest, and death have been reported. Some of these agents, particularly ephedra alkaloids (ephedrine, ma huang, phenylpropanolamine), may also predispose patients to hemorrhagic and ischemic stroke. Therapy with sympathomimetic agents should generally be avoided or administered cautiously in patients with sensitivity to sympathomimetic amines, hyperthyroidism, or underlying cardiovascular or cerebrovascular disorders. These agents should not be used in patients with severe coronary artery disease or severe/uncontrolled hypertension.
Diabetes Mellitus
Moderate:
GDP-EX
The phenylephrine in GDP-EX has a moderate potential interaction with Diabetes Mellitus.
Sympathomimetic agents may cause increases in blood glucose concentrations. These effects are usually transient and slight but may be significant with dosages higher than those normally recommended. Therapy with sympathomimetic agents should be administered cautiously in patients with diabetes mellitus. Closer monitoring of blood glucose concentrations may be appropriate.
Glaucoma/Intraocular Hypertension
Moderate:
GDP-EX
The phenylephrine in GDP-EX has a moderate potential interaction with Glaucoma/Intraocular Hypertension.
Sympathomimetic agents can induce transient mydriasis via stimulation of alpha-1 adrenergic receptors. In patients with anatomically narrow angles or narrow-angle glaucoma, pupillary dilation can provoke an acute attack. In patients with other forms of glaucoma, mydriasis may occasionally increase intraocular pressure. Therapy with sympathomimetic agents should be administered cautiously in patients with or predisposed to glaucoma, particularly narrow-angle glaucoma.
Hyperthyroidism
Major:
GDP-EX
The phenylephrine in GDP-EX has a major potential interaction with Hyperthyroidism.
Sympathomimetic agents may cause adverse cardiovascular effects, particularly when used in high dosages and/or in susceptible patients. In cardiac tissues, these agents may produce positive chronotropic and inotropic effects via stimulation of beta- 1 adrenergic receptors. Cardiac output, oxygen consumption, and the work of the heart may be increased. In the peripheral vasculature, vasoconstriction may occur via stimulation of alpha-1 adrenergic receptors. Palpitations, tachycardia, arrhythmia, hypertension, reflex bradycardia, coronary occlusion, cerebral vasculitis, myocardial infarction, cardiac arrest, and death have been reported. Some of these agents, particularly ephedra alkaloids (ephedrine, ma huang, phenylpropanolamine), may also predispose patients to hemorrhagic and ischemic stroke. Therapy with sympathomimetic agents should generally be avoided or administered cautiously in patients with sensitivity to sympathomimetic amines, hyperthyroidism, or underlying cardiovascular or cerebrovascular disorders. These agents should not be used in patients with severe coronary artery disease or severe/uncontrolled hypertension.
Infection
Moderate:
elranatamab
Elranatamab has a moderate potential interaction with Infection.
Elranatamab can cause serious and fatal infections. Patients should be evaluated for active infection before and during treatment with elranatamab, and administration should be avoided if infection is detected.
Liver Disease
Moderate:
elranatamab
Elranatamab has a moderate potential interaction with Liver Disease.
Elranatamab can cause increased levels of liver enzymes and bilirubin. The effect of moderate to severe hepatic impairment (total bilirubin >1.5 times ULN and any AST) on the pharmacokinetics of elranatamab has not been evaluated.
Pheochromocytoma
Major:
GDP-EX
The phenylephrine in GDP-EX has a major potential interaction with Pheochromocytoma.
Sympathomimetic agents may cause adverse cardiovascular effects, particularly when used in high dosages and/or in susceptible patients. In cardiac tissues, these agents may produce positive chronotropic and inotropic effects via stimulation of beta- 1 adrenergic receptors. Cardiac output, oxygen consumption, and the work of the heart may be increased. In the peripheral vasculature, vasoconstriction may occur via stimulation of alpha-1 adrenergic receptors. Palpitations, tachycardia, arrhythmia, hypertension, reflex bradycardia, coronary occlusion, cerebral vasculitis, myocardial infarction, cardiac arrest, and death have been reported. Some of these agents, particularly ephedra alkaloids (ephedrine, ma huang, phenylpropanolamine), may also predispose patients to hemorrhagic and ischemic stroke. Therapy with sympathomimetic agents should generally be avoided or administered cautiously in patients with sensitivity to sympathomimetic amines, hyperthyroidism, or underlying cardiovascular or cerebrovascular disorders. These agents should not be used in patients with severe coronary artery disease or severe/uncontrolled hypertension.
Prostate Tumor, Benign
Moderate:
GDP-EX
The phenylephrine in GDP-EX has a moderate potential interaction with Prostate Tumor, Benign.
Sympathomimetic agents may cause or worsen urinary difficulty in patients with prostate enlargement due to smooth muscle contraction in the bladder neck via stimulation of alpha-1 adrenergic receptors. Therapy with sympathomimetic agents should be administered cautiously in patients with hypertrophy or neoplasm of the prostate.
Renal Dysfunction
Moderate:
elranatamab
Elranatamab has a moderate potential interaction with Renal Dysfunction.
The pharmacokinetics of elranatamab have not been studied in patients with severe renal impairment and end-stage renal disease.
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More resources
elranatamab
A total of 484 drugs are known to interact with elranatamab.
- Elranatamab is in the drug class bispecific T-cell engagers (BiTE).
- Elranatamab is used to treat Multiple Myeloma.
GDP-EX
A total of 546 drugs are known to interact with GDP-EX.
- Gdp-ex is in the drug class upper respiratory combinations.
- Gdp-ex is used to treat Cough and Nasal Congestion.
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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