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Drug Interactions between Ritalin and Tenex

This report displays the potential drug interactions for the following 2 drugs:

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Interactions between your drugs

Moderate

guanFACINE methylphenidate

Applies to: Tenex (guanfacine) and Ritalin (methylphenidate)

MONITOR: Serious adverse events may occur during concomitant use of methylphenidate or dexmethylphenidate with centrally-acting alpha-2 agonists. The mechanism of interaction, if any, is unknown, and a causal relationship has not been established. The use of clonidine, with or without methylphenidate, has been associated with rare cases of sudden death and cardiotoxicity including sinus bradycardia and heart block. Electrocardiographic (ECG) abnormalities have also been demonstrated in patients treated with clonidine, even at low dosages. However, some investigators suggest these findings may reflect the pharmacologic effects of the drug and not necessarily cardiotoxic effects. Although the existence of a methylphenidate-clonidine interaction is questionable, it is possible that the combination may be more dangerous than either drug alone with respect to drug discontinuation. Specifically, methylphenidate may exacerbate the rebound hypertension and hyperadrenergic state associated with abrupt withdrawal of clonidine, and methylphenidate withdrawal may aggravate the bradycardia and hypotension associated with clonidine use.

MANAGEMENT: The safety of using methylphenidate (racemic) or dexmethylphenidate (the more pharmacologically active d-enantiomer) in combination with clonidine or other centrally-acting alpha-2 agonists has not been established. Patients being considered for alpha-2 agonist therapy, alone or with methylphenidate or dexmethylphenidate, should have cardiovascular status and history evaluated. Vital signs, including pulse and blood pressure, should be monitored prior to and during therapy. The routine use of ECGs in patients being treated for behavioral disorders is controversial, since it is uncertain what findings may indicate actual risk for sudden death. However, ECG monitoring may be appropriate in cases of preexisting cardiac disease or abnormal finding on physical examination. Finally, patients should be advised not to abruptly discontinue the alpha-2 agonist, methylphenidate, or dexmethylphenidate following chronic use unless otherwise directed by their physician.

References

  1. Roden DM, Nadeau JH, Primm RK "Electrophysiologic and hemodynamic effects of chronic oral therapy with the alpha 2-agonists clonidine and tiamenidine in hypertensive volunteers." Clin Pharmacol Ther 43 (1988): 648-54
  2. Brest AN "Hemodynamic and cardiac effects of clonidine." J Cardiovasc Pharmacol 2 (1980): s39-46
  3. Maloney MJ, Schwam SJ "Clonidine and sudden death." Pediatrics 96 (1995): 1176-7
  4. "Product Information. Ritalin (methylphenidate)." Novartis Pharmaceuticals PROD (2001):
  5. "Product Information. Focalin (dexmethylphenidate)." Mikart Inc (2001):
  6. Blackman JA, Samson-Fang L, Gutgesell H "Clonidine and electrocardiograms." Pediatrics 98((6 Pt 1)) (1996): 1223-4
  7. Wilens TE, Spencer TJ, Swanson JM, Connor DF, Cantwell D "Combining methylphenidate and clonidine: a clinically sound medication." J Am Acad Child Adolesc Psychiatry 38 (1999): 614-9; discussion 619-22
  8. Popper CW "Combining methylphenidate and clonidine: pharmacologic questions and news reports about sudden death." J Child Adolesc Psychopharmacol 5 (1995): 157-66
  9. Swanson JM, Flockhart D, Udrea D, Cantwell D, Connor D, Williams L "Clonidine in the treatment of ADHD: questions about safety and efficacy." J Child Adolesc Psychopharmacol 5 (1995): 301-4
View all 9 references

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Drug and food interactions

Major

guanFACINE food

Applies to: Tenex (guanfacine)

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations of guanfacine. The risk of adverse reactions such as hypotension, bradycardia, and sedation may increase. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit. Ketoconazole, a potent CYP450 3A4 inhibitor, has been reported to increase guanfacine peak plasma concentration (Cmax) and systemic exposure (AUC) by approximately 2- and 3-fold, respectively. A computer simulation suggests that fluconazole, a moderate CYP450 3A4 inhibitor, would increase guanfacine Cmax and AUC by about 1.5- and 2-fold, respectively. 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.

GENERALLY AVOID: Alcohol may enhance the sedative and hypotensive effects of guanfacine.

GENERALLY AVOID: Administration of extended-release guanfacine with a high-fat meal may increase the bioavailability of guanfacine. When a single 4 mg dose of extended-release guanfacine was administered to adult volunteers with a high-fat breakfast, mean guanfacine peak plasma concentration (Cmax) and systemic exposure (AUC) increased by approximately 75% and 40%, respectively, compared to dosing in a fasted state.

MANAGEMENT: Patients treated with guanfacine should avoid consumption of grapefruit and grapefruit juice. In addition, it is preferable to avoid or limit the use of alcohol during treatment. Patients should be advised against driving or operating hazardous machinery until they know how the medication affects them. The extended-release formulation of guanfacine should not be taken together with a high-fat meal.

References

  1. "Product Information. Tenex (guanfacine)." Wyeth-Ayerst Laboratories PROD (2001):
  2. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  3. "Product Information. Intuniv (guanfacine)." Shire US Inc (2009):

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Moderate

methylphenidate food

Applies to: Ritalin (methylphenidate)

GENERALLY AVOID: Alcohol may exacerbate the adverse central nervous system effects of psychoactive drugs, including methylphenidate.

GENERALLY AVOID: Consumption of alcohol while taking certain sustained-release formulations of methylphenidate may cause rapid release of the drug, resulting in increased systemic levels of methylphenidate. In vitro studies have been conducted using Metadate CD 60 mg and Ritalin LA 40 mg capsules, as well as Concerta 18 mg tablet. At an alcohol concentration of 40%, an increase in the release rate of methylphenidate was observed in the first hour for Metadate CD and Ritalin LA, resulting in 84% and 98% of the methylphenidate being released, respectively. In contrast, there was no increased release of methylphenidate in the first hour for Concerta. These results are considered to be representative of the other available strengths of the corresponding product.

MANAGEMENT: Patients treated with methylphenidate should be advised to avoid alcohol or medications that contain alcohol.

References

  1. "Product Information. Metadate CD (methylphenidate)." Celltech Pharmaceuticals Inc (2022):
  2. "Product Information. Concerta (methylphenidate)." Alza (2002):
  3. "Product Information. Ritalin LA (methylphenidate)." Quality Care Products/Lake Erie Medical (2013):

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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

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Drug Interaction Classification

These classifications are only a guideline. The relevance of a particular drug interaction to a specific individual is difficult to determine. Always consult your healthcare provider before starting or stopping any medication.
Major Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.
Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.
Minor 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.
Unknown No interaction information available.

Further information

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