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Drug Interactions between MSP-Blu and phentermine / topiramate

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

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Interactions between your drugs

Major

phentermine methylene blue

Applies to: phentermine / topiramate and MSP-Blu (hyoscyamine / methenamine / methylene blue / phenyl salicylate)

CONTRAINDICATED: Centrally-acting sympathomimetic agents (i.e., CNS stimulants), particularly the amphetamines and amphetamine derivatives, may precipitate severe hypertensive reactions and hyperpyrexia in patients treated with monoamine oxidase inhibitors (MAOIs). Death has occurred in some reported cases. The mechanism involves a synergistic sympathomimetic effect due to enhanced norepinephrine storage in adrenergic neurons (MAOI activity) and increased liberation or decreased reuptake of catecholamines (central sympathomimetic activity). MAOIs also slow amphetamine metabolism, which may potentiate amphetamine effect on the release of norepinephrine and other monoamines from adrenergic nerve endings.

MANAGEMENT: In general, CNS stimulants should not be used concurrently with MAOIs or other agents that possess MAOI activity (e.g., furazolidone, linezolid, methylene blue, procarbazine). At least 14 days should elapse between discontinuation of MAOI therapy and initiation of treatment with CNS stimulants.

References

  1. Pettinger WA, Soyangco FG, Oates JA (1968) "Inhibition of monoamine oxidase in man by furazolidone." Clin Pharmacol Ther, 9, p. 442-7
  2. Schulz R, Antonin KH, Hoffmann E, et al. (1989) "Tyramine kinetics and pressor sensitivity during monoamine oxidase inhibition by selegiline." Clin Pharmacol Ther, 46, p. 528-36
  3. Krisko I, Lewis E, Johnson JE (1969) "Severe hyperpyrexia due to tranylcypromine-amphetamine toxicity." Ann Intern Med, 70, p. 559-64
  4. Elis J, Laurence DR, Mattie H, Prichard BN (1967) "Modification by monoamine oxidase inhibitors of the effect of some sympathomimetics on blood pressure." Br Med J, 2, p. 75-8
  5. Goldberg LI (1964) "Monoamine oxidase inhibitors: adverse reactions and possible mechanisms." JAMA, 190, p. 456-62
  6. Sjoqvist F (1965) "Psychotropic drugs (2) interaction between monoamine oxidase (MAO) inhibitors and other substances." Proc R Soc Med, 58, p. 967-78
  7. Harrison WM, McGrath PJ, Stewart JW, Quitkin F (1989) "MAOIs and hypertensive crises: the role of OTC drugs." J Clin Psychiatry, 50, p. 64-5
  8. Wright SP (1978) "Hazards with monoamine-oxidase inhibitors: a persistent problem." Lancet, 1, p. 284-5
  9. Boakes AJ, Laurence DR, Teoh PC, Barar FS, Benedikter LT, Pritchard BN (1973) "Interactions between sympathomimetic amines and antidepressant agents in man." Br Med J, 1, p. 311-5
  10. Dally PJ (1962) "Fatal reaction associated with tranylcypromine and methylamphetamine." Lancet, 1, p. 1235-6
  11. Schildkraut JJ, Klerman GL, Friend DG, Greenblatt M (1963) "Biochemical and pressor effects of oral d,l-dihydroxyphenylalanine in patients pretreated with antidepressant drugs." Ann N Y Acad Sci, 107, p. 1005-15
  12. Smookler S, Bermudez AJ (1982) "Hypertensive crisis resulting from an MAO inhibitor and an over-the-counter appetite suppressant." Ann Intern Med, 11, p. 482-4
  13. Ban TA (1975) "Drug interactions with psychoactive drugs." Dis Nerv Syst, 36, p. 164-6
  14. Darcy PF, Griffin JP (1995) "Interactions with drugs used in the treatment of depressive illness." Adverse Drug React Toxicol Rev, 14, p. 211-31
  15. De Vita VT, Hahn MA, Oliverio VT (1965) "Monoamine oxidase inhibition by a new carcinostatic agent, n-isopropyl-a-(2-methylhydrazino)-p-toluamide (MIH). (30590)." Proc Soc Exp Biol Med, 120, p. 561-5
  16. (2001) "Product Information. Ritalin (methylphenidate)." Novartis Pharmaceuticals
  17. (2001) "Product Information. Dexedrine (dextroamphetamine)." SmithKline Beecham
  18. (2001) "Product Information. Adderall (amphetamine-dextroamphetamine)." Shire Richwood Pharmaceutical Company Inc
  19. Markowitz JS, Patrick KS (2001) "Pharmacokinetic and pharmacodynamic drug interactions in the treatment of attention-deficit hyperactivity disorder." Clin Pharmacokinet, 40, p. 753-72
  20. (2001) "Product Information. Focalin (dexmethylphenidate)." Mikart Inc
  21. (2002) "Product Information. Strattera (atomoxetine)." Lilly, Eli and Company
  22. (2007) "Product Information. Vyvanse (lisdexamfetamine)." Shire US Inc
View all 22 references

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Major

hyoscyamine topiramate

Applies to: MSP-Blu (hyoscyamine / methenamine / methylene blue / phenyl salicylate) and phentermine / topiramate

MONITOR CLOSELY: Certain drugs such as carbonic anhydrase inhibitors and drugs with anticholinergic activity (e.g., antihistamines, antispasmodics, neuroleptics, phenothiazines, skeletal muscle relaxants, tricyclic antidepressants, disopyramide) may potentiate the risk of oligohidrosis and hyperthermia associated occasionally with the use of topiramate, particularly in pediatric patients. These agents may alter electrolyte and fluid balance (carbonic anhydrase inhibition), inhibit peripheral sweating mechanisms (anticholinergic effect), and/or interfere with core body temperature regulation in the hypothalamus (neuroleptics and phenothiazines), resulting in the inability to adjust to temperature changes, especially in hot weather. Also, agents with anticholinergic activity frequently cause drowsiness and other central nervous system-depressant effects, which may be additively or synergistically increased in patients also treated with topiramate.

MANAGEMENT: Caution is advised when topiramate is prescribed with other drugs that predispose patients to heat-related disorders, including carbonic anhydrase inhibitors and drugs with anticholinergic activity. Patients, particularly pediatric patients, should be monitored closely for evidence of decreased sweating and increased body temperature, especially in warm or hot weather. Proper hydration before and during vigorous activities or exposure to warm temperatures is recommended. Patients (or their guardians or caregivers) should contact their physician immediately if they are not sweating as usual, with or without a fever. Ambulatory patients treated with topiramate and agents with anticholinergic activity should also be made aware of the possibility of additive CNS effects (e.g., drowsiness, dizziness, lightheadedness, confusion) and counseled to avoid activities requiring mental alertness until they know how these agents affect them.

References

  1. (2001) "Product Information. Topamax (topiramate)." Ortho McNeil Pharmaceutical

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Moderate

phentermine topiramate

Applies to: phentermine / topiramate and phentermine / topiramate

MONITOR: Coadministration with topiramate may increase the plasma concentrations of phentermine. The exact mechanism of interaction has not been established. When a single 15 mg dose of phentermine was administered with a 92 mg dose of topiramate, phentermine peak plasma concentration (Cmax) and systemic exposure (AUC) increased by 13% and 42%, respectively, compared to phentermine administered alone. No significant changes were observed in the pharmacokinetics of topiramate.

MANAGEMENT: Caution is advised when phentermine is used in combination with topiramate. Patients should be monitored for potentially increased adverse effects of phentermine such as dizziness, restlessness, insomnia, tremor, headache, euphoria, dysphoria, palpitation, tachycardia, and blood pressure elevation.

References

  1. (2001) "Product Information. Ionamin (phentermine)." Rhone Poulenc Rorer

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Drug and food interactions

Moderate

phentermine food

Applies to: phentermine / topiramate

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 (1995) "Methamphetamine and ethanol interactions in humans." Clin Pharmacol Ther, 57, p. 559-68
  2. (2001) "Product Information. Didrex (benzphetamine)." Pharmacia and Upjohn
  3. (2012) "Product Information. Suprenza (phentermine)." Akrimax Pharmaceuticals

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Moderate

hyoscyamine food

Applies to: MSP-Blu (hyoscyamine / methenamine / methylene blue / phenyl salicylate)

GENERALLY AVOID: Use of anticholinergic agents with alcohol may result in sufficient impairment of attention so as to render driving and operating machinery more hazardous. In addition, the potential for abuse may be increased with the combination. The mechanism of interaction is not established but may involve additive depressant effects on the central nervous system. No effect of oral propantheline or atropine on blood alcohol levels was observed in healthy volunteers when administered before ingestion of a standard ethanol load. However, one study found impairment of attention in subjects given atropine 0.5 mg or glycopyrrolate 1 mg in combination with alcohol.

MANAGEMENT: Alcohol should generally be avoided during therapy with anticholinergic agents. Patients should be counseled to avoid activities requiring mental alertness until they know how these agents affect them.

References

  1. Linnoila M (1973) "Drug effects on psychomotor skills related to driving: interaction of atropine, glycopyrrhonium and alcohol." Eur J Clin Pharmacol, 6, p. 107-12

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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.

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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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