Interactions between Despec DM Syrup and Pralsetinib
1 drug interaction and 18 additional warnings found for the following 2 drugs:
- Despec DM Syrup (dextromethorphan/guaifenesin/phenylephrine)
- pralsetinib
Drug interactions
Moderate drug interactions
Moderate:
dextromethorphan pralsetinib
Applies to: Despec DM Syrup (dextromethorphan / guaifenesin / phenylephrine) and pralsetinib
Monitor
Coadministration with pralsetinib may alter the plasma concentrations of drugs that are substrates of CYP450 2C8, 2C9, 3A4, and/or 3A5. In vitro studies indicate that pralsetinib is both an inhibitor as well as an inducer of CYP450 2C8, 2C9, 3A4, and 3A5. Therefore, pralsetinib may decrease clearance via inhibition or increase clearance via induction of these isoenzymes, resulting in increased or decreased plasma concentrations of agents that are metabolized by one or more of these isoenzymes. Clinical and pharmacokinetic data are currently lacking.
Management
Caution is advised if pralsetinib is used concomitantly with drugs that are substrates of CYP450 2C8, 2C9, 3A4, and/or 3A5, particularly sensitive substrates or those with a narrow therapeutic range. Some authorities recommend avoiding coadministration of pralsetinib with CYP450 2C8, 2C9, 3A4, and/or 3A5 substrates for which minimal concentration changes may lead to therapeutic failure or serious toxicities. If coadministration is required, dosage adjustments as well as clinical and laboratory monitoring may be appropriate whenever pralsetinib is added to or withdrawn from therapy. The prescribing information for concomitant medications should be consulted to assess the benefits versus risks of coadministration and for any dosage adjustments that may be required.
References (4)
- (2023) "Product Information. Gavreto (pralsetinib)." Roche Products Pty Ltd, GAVRETO 20230406
- (2023) "Product Information. Gavreto (pralsetinib)." Roche Products Ltd
- (2023) "Product Information. Gavreto (pralsetinib)." Genentech
- (2021) "Product Information. Gavreto (pralsetinib)." Hoffmann-La Roche Limited
Food/lifestyle interactions
Major food/lifestyle interactions
Major:
pralsetinib Food/Lifestyle
Applies to: pralsetinib
Adjust dosing interval
Food significantly increases the oral bioavailability of pralsetinib. According to the product labeling, administration of pralsetinib (200 mg) with a high-fat meal (approximately 800 to 1000 calories; 50% to 60% from fat) increased mean pralsetinib peak plasma concentration (Cmax) and systemic exposure (AUC) by 104% and 122%, respectively. The median time to maximum concentration (Tmax) was delayed from 4 hours to 8.5 hours, when compared to the fasted state.
Generally avoid
The juice of grapefruit and/or Seville oranges may increase the plasma concentrations of pralsetinib. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit and Seville oranges. In general, the effect of grapefruit juice is concentration-, dose- and preparation-dependent, and can vary widely among brands. Certain preparations of grapefruit juice (e.g., high dose, double strength) have sometimes demonstrated potent inhibition of CYP450 3A4, while other preparations (e.g., low dose, single strength) have typically demonstrated moderate inhibition. Increased exposure to pralsetinib may increase the risk of adverse effects such as interstitial lung disease/pneumonitis, liver transaminase elevations, hypertension, and hemorrhage. Some clinical trials have also observed prolongation of the QT interval in patients on pralsetinib, though this was not observed in a study of 34 patients with rearranged during transfection (RET)-altered solid tumors on pralsetinib at the recommended dosage.
Management
Pralsetinib should be administered on an empty stomach, with no food intake recommended for at least 2 hours before and at least 1 hour after taking the medication. Patients should avoid consumption of grapefruit, grapefruit juice, Seville oranges, or Seville orange juice during treatment with pralsetinib.
References (4)
- (2023) "Product Information. Gavreto (pralsetinib)." Roche Products Pty Ltd, GAVRETO 20230406
- (2024) "Product Information. Gavreto (pralsetinib)." Genentech
- (2024) "Product Information. Gavreto (pralsetinib)." Roche Products Ltd
- (2024) "Product Information. Gavreto (pralsetinib)." Hoffmann-La Roche Limited
Moderate food/lifestyle interactions
Moderate:
dextromethorphan Food/Lifestyle
Applies to: Despec DM Syrup (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: Despec DM Syrup (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
15 potential interactions Applies to: 15 conditions, including High Blood Pressure, Benign Prostatic Hyperplasia, Hypokalemia, Hyperthyroidism, and Hypocalcemia.
Benign Prostatic Hyperplasia
Moderate:
Despec DM Syrup
The phenylephrine in Despec DM Syrup 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:
Despec DM Syrup
The phenylephrine in Despec DM Syrup 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:
Despec DM Syrup
The phenylephrine in Despec DM Syrup 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:
Despec DM Syrup
The phenylephrine in Despec DM Syrup 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:
Despec DM Syrup
The phenylephrine in Despec DM Syrup 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.
High Blood Pressure
Moderate:
pralsetinib
Pralsetinib has a moderate potential interaction with High Blood Pressure.
Hypertension has been reported in patients in treatment with pralsetinib. This drug should not be initiated in patients with uncontrolled hypertension. Caution and close monitoring is advised.
Hyperthyroidism
Major:
Despec DM Syrup
The phenylephrine in Despec DM Syrup 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.
Hypocalcemia
Moderate:
pralsetinib
Pralsetinib has a moderate potential interaction with Hypocalcemia.
QT prolongation was reported in clinical trials in patients that received pralsetinib. Use with caution in patients with history of arrhythmias, QT prolongation or taking medications that can prolong the QT interval (e.g., strong CYP450 3A4 inhibitors). Monitor QT interval and serum electrolytes before initiation and regularly during treatment. Hypokalemia, hypomagnesemia, and hypocalcemia should be corrected prior and during treatment.
Hypokalemia
Moderate:
pralsetinib
Pralsetinib has a moderate potential interaction with Hypokalemia.
QT prolongation was reported in clinical trials in patients that received pralsetinib. Use with caution in patients with history of arrhythmias, QT prolongation or taking medications that can prolong the QT interval (e.g., strong CYP450 3A4 inhibitors). Monitor QT interval and serum electrolytes before initiation and regularly during treatment. Hypokalemia, hypomagnesemia, and hypocalcemia should be corrected prior and during treatment.
Liver Disease
Moderate:
pralsetinib
Pralsetinib has a moderate potential interaction with Liver Disease.
Pralsetinib has not been studied in patients with moderate or severe hepatic impairment. Additionally, clinical trials reported hepatotoxicity in some patients receiving treatment. Caution and close monitoring is advised if administering in patients with hepatic impairment.
Long QT Syndrome
Moderate:
pralsetinib
Pralsetinib has a moderate potential interaction with Long QT Syndrome.
QT prolongation was reported in clinical trials in patients that received pralsetinib. Use with caution in patients with history of arrhythmias, QT prolongation or taking medications that can prolong the QT interval (e.g., strong CYP450 3A4 inhibitors). Monitor QT interval and serum electrolytes before initiation and regularly during treatment. Hypokalemia, hypomagnesemia, and hypocalcemia should be corrected prior and during treatment.
Magnesium Imbalance
Moderate:
pralsetinib
Pralsetinib has a moderate potential interaction with Magnesium Imbalance.
QT prolongation was reported in clinical trials in patients that received pralsetinib. Use with caution in patients with history of arrhythmias, QT prolongation or taking medications that can prolong the QT interval (e.g., strong CYP450 3A4 inhibitors). Monitor QT interval and serum electrolytes before initiation and regularly during treatment. Hypokalemia, hypomagnesemia, and hypocalcemia should be corrected prior and during treatment.
Pheochromocytoma
Major:
Despec DM Syrup
The phenylephrine in Despec DM Syrup 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:
Despec DM Syrup
The phenylephrine in Despec DM Syrup 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:
pralsetinib
Pralsetinib has a moderate potential interaction with Renal Dysfunction.
Pralsetinib has not been studied in patients with severe renal impairment or end-stage renal disease. Caution is advised if administering in these patients.
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Despec DM Syrup
A total of 546 drugs are known to interact with Despec DM Syrup.
- Despec dm syrup is in the drug class upper respiratory combinations.
- Despec dm syrup is used to treat Cough and Nasal Congestion.
pralsetinib
A total of 740 drugs are known to interact with pralsetinib.
- Pralsetinib is in the drug class multikinase inhibitors.
- Pralsetinib is used to treat the following conditions:
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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