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Drug Interactions between Cystemms-V and Fansidar

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

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Interactions between your drugs

Major

methenamine sulfadoxine

Applies to: Cystemms-V (hyoscyamine / methenamine / methylene blue / phenyl salicylate) and Fansidar (pyrimethamine / sulfadoxine)

CONTRAINDICATED: Some sulfonamides can form an insoluble precipitate with formaldehyde, which is generated from the hydrolysis of methenamine in acidic urine maintained by the presence of hippuric acid.

MANAGEMENT: Methenamine preparations should not be given to patients taking sulfonamides due to the risk of crystalluria. An alkalinizing agent should not be added because this may render methenamine less effective.

References

  1. (2001) "Product Information. Urised (methenamine)." Polymedica Pharmaceuticals USA Inc
  2. (2002) "Product Information. Hiprex (methenamine)." Hoechst Marion Roussel

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Moderate

pyrimethamine sulfadoxine

Applies to: Fansidar (pyrimethamine / sulfadoxine) and Fansidar (pyrimethamine / sulfadoxine)

MONITOR: Coadministration of pyrimethamine in doses exceeding 25 mg per week with trimethoprim or sulfonamides may increase the risk of megaloblastic anemia and pancytopenia. The proposed mechanism is additive antifolate effects.

MANAGEMENT: Periodic clinical and laboratory monitoring for signs of folic acid deficiency and hematologic changes is advisable.

References

  1. "Multum Information Services, Inc. Expert Review Panel"
  2. Cerner Multum, Inc. "UK Summary of Product Characteristics."

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Drug and food interactions

Moderate

hyoscyamine food

Applies to: Cystemms-V (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.

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

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

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