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Drug Interaction Report

5 potential interactions and/or warnings found for the following 2 drugs:

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Interactions between your drugs

Moderate

phentermine modafinil

Applies to: phentermine, Provigil (modafinil)

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

  1. Rosenblatt JE, Lake CR, van Kammen DP, Ziegler MG, Bunney WE Jr. Interactions of amphetamine, pimozide, and lithium on plasma norepineophrine and dopamine-beta-hydroxylase in schizophrenic patients. Psychiatry Res. 1979;1:45-52.
  2. Cavanaugh JH, Griffith JD, Oates JA. Effect of amphetamine on the pressor response to tyramine: formation of p-hydroxynorephedrine from amphetamine in man. Clin Pharmacol Ther. 1970;11:656.
  3. Product Information. Adderall (amphetamine-dextroamphetamine). Shire Richwood Pharmaceutical Company Inc. 2001;PROD.
  4. Product Information. Tenuate (diethylpropion). Aventis Pharmaceuticals. 2001;PROD.
  5. Product Information. Sanorex (mazindol). Novartis Pharmaceuticals. 2001;PROD.
  6. Product Information. Focalin (dexmethylphenidate). Mikart Inc. 2001.
  7. Product Information. Strattera (atomoxetine). Lilly, Eli and Company. 2002.
View all 7 references

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Drug and food interactions

Moderate

phentermine food

Applies to: phentermine

GENERALLY AVOID: Alcohol may potentiate the central nervous system and cardiovascular effects of centrally-acting appetite suppressants. In one study, concurrent administration of methamphetamine (30 mg intravenously) and ethanol (1 gm/kg orally over 30 minutes) increased heart rate by 24 beats/minute compared to methamphetamine alone. This increases cardiac work and myocardial oxygen consumption, which may lead to more adverse cardiovascular effects than either agent alone. Subjective effects of ethanol were diminished in the eight study subjects, but those of methamphetamine were not affected. The pharmacokinetics of methamphetamine were also unaffected except for a decrease in the apparent volume of distribution at steady state.

MANAGEMENT: Concomitant use of centrally-acting appetite suppressants and alcohol should be avoided if possible, especially in patients with a history of cardiovascular disease. Patients should be counselled 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

  1. Mendelson J, Jones RT, Upton R, Jacob P 3rd. Methamphetamine and ethanol interactions in humans. Clin Pharmacol Ther. 1995;57:559-68.
  2. Product Information. Didrex (benzphetamine). Pharmacia and Upjohn. 2001;PROD.
  3. Product Information. Suprenza (phentermine). Akrimax Pharmaceuticals. 2012.

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Minor

modafinil food

Applies to: Provigil (modafinil)

Administration with food may delay the absorption of modafinil (the racemate) and armodafinil (the R-enantiomer) without significantly affecting their overall bioavailability. According to the product labeling, modafinil's absorption may be delayed by approximately one hour if taken with food. Similarly, the time to reach peak plasma concentration (Tmax) of armodafinil may be delayed by approximately 2 to 4 hours in the fed state.

References

  1. Product Information. Provigil (modafinil). Cephalon, Inc. 2001;PROD.
  2. Product Information. Nuvigil (armodafinil). Cephalon Inc. 2007.

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Therapeutic duplication warnings

Therapeutic duplication is the use of more than one medicine from the same drug category or therapeutic class to treat the same condition. This can be intentional in cases where drugs with similar actions are used together for demonstrated therapeutic benefit. It can also be unintentional in cases where a patient has been treated by more than one doctor, or had prescriptions filled at more than one pharmacy, and can have potentially adverse consequences.

Duplication

Stimulants

Therapeutic duplication

The recommended maximum number of medicines in the 'stimulants' category to be taken concurrently is usually one. Your list includes two medicines belonging to the 'stimulants' category:

  • phentermine
  • Provigil (modafinil)

Note: In certain circumstances, the benefits of taking this combination of drugs may outweigh any risks. Always consult your healthcare provider before making changes to your medications or dosage.

Duplication

Cerebral stimulants

Therapeutic duplication

The recommended maximum number of medicines in the 'cerebral stimulants' category to be taken concurrently is usually one. Your list includes two medicines belonging to the 'cerebral stimulants' category:

  • phentermine
  • Provigil (modafinil)

Note: In certain circumstances, the benefits of taking this combination of drugs may outweigh any risks. Always consult your healthcare provider before making changes to your medications or dosage.

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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.

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Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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