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Drug Interactions between aspirin / butalbital and emtricitabine / nelfinavir / tenofovir

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

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Interactions between your drugs

Moderate

butalbital nelfinavir

Applies to: aspirin / butalbital and emtricitabine / nelfinavir / tenofovir

MONITOR: Coadministration with drugs that are inducers of CYP450 3A4 may decrease the plasma concentrations of protease inhibitors (PIs), which are primarily metabolized by the isoenzyme.

MANAGEMENT: Given the risk of reduced viral susceptibility and resistance development associated with subtherapeutic antiretroviral drug levels, protease inhibitors should be used cautiously with agents that induce CYP450 3A4, particularly if only one PI is used in the antiretroviral regimen. Coadministration of atazanavir without ritonavir and carbamazepine, phenobarbital, or phenytoin is not recommended. Antiretroviral response should be monitored more closely whenever a CYP450 3A4 inducer is added to or withdrawn from therapy, and the antiretroviral regimen adjusted as necessary.

References

  1. "Product Information. Invirase (saquinavir)." Roche Laboratories PROD (2001):
  2. "Product Information. Crixivan (indinavir)." Merck & Co., Inc PROD (2001):
  3. "Product Information. Viracept (nelfinavir)." Agouron Pharma Inc PROD (2001):
  4. Brooks J, Daily J, Schwamm L "Protease inhibitors and anticonvulsants." AIDS Clin Care 9 (1997): 87,90
  5. Barry M, Gibbons S, Back D, Mulcahy F "Protease inhibitors in patients with HIV disease. Clinically important pharmacokinetic considerations." Clin Pharmacokinet 32 (1997): 194-209
  6. "Product Information. Agenerase (amprenavir)." Glaxo Wellcome PROD (2001):
  7. Acosta EP, Henry K, Baken L, Page LM, Fletcher CV "Indinavir concentrations and antiviral effect." Pharmacotherapy 19 (1999): 708-12
  8. Sommadossi JP "HIV protease inhibitors: pharmacologic and metabolic distinctions." AIDS 13 (1999): s29-40
  9. Hugen PWH, Burger DM, Brinkman K, terHofstede HJM, Schuurman R, Koopmans PP, Hekster YA "Carbamazepine-indinavir interaction causes antiretroviral therapy failure." Ann Pharmacother 34 (2000): 465-70
  10. Durant J, Clevenbergh P, Garraffo R, Halfon P, Icard S, DelGiudice P, Montagne N, Schapiro JM, Dellamonica P "Importance of protease inhibitor plasma levels in HIV-infected patients treated with genotypic-guided therapy: pharmacological data from the Viradapt Study." Aids 14 (2000): 1333-9
  11. "Product Information. Fortovase (saquinavir)." Roche Laboratories PROD (2001):
  12. "Product Information. Reyataz (atazanavir)." Bristol-Myers Squibb (2003):
  13. "Product Information. Lexiva (fosamprenavir)." GlaxoSmithKline (2003):
  14. Liedtke MD, Lockhart SM, Rathbun RC "Anticonvulsant and antiretroviral interactions." Ann Pharmacother 38 (2004): 482-9
  15. "Product Information. Aptivus (tipranavir)." Boehringer-Ingelheim (2005):
  16. "Product Information. Prezista (darunavir)." Ortho Biotech Inc (2006):
  17. Canadian Pharmacists Association "e-CPS. http://www.pharmacists.ca/function/Subscriptions/ecps.cfm?link=eCPS_quikLink" (2006):
View all 17 references

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Drug and food interactions

Major

butalbital food

Applies to: aspirin / butalbital

GENERALLY AVOID: Concurrent acute use of barbiturates and ethanol may result in additive CNS effects, including impaired coordination, sedation, and death. Tolerance of these agents may occur with chronic use. The mechanism is related to inhibition of microsomal enzymes acutely and induction of hepatic microsomal enzymes chronically.

MANAGEMENT: The combination of ethanol and barbiturates should be avoided.

References

  1. Gupta RC, Kofoed J "Toxological statistics for barbiturates, other sedatives, and tranquilizers in Ontario: a 10-year survey." Can Med Assoc J 94 (1966): 863-5
  2. Misra PS, Lefevre A, Ishii H, Rubin E, Lieber CS "Increase of ethanol, meprobamate and pentobarbital metabolism after chronic ethanol administration in man and in rats." Am J Med 51 (1971): 346-51
  3. Saario I, Linnoila M "Effect of subacute treatment with hypnotics, alone or in combination with alcohol, on psychomotor skills related to driving." Acta Pharmacol Toxicol (Copenh) 38 (1976): 382-92
  4. Stead AH, Moffat AC "Quantification of the interaction between barbiturates and alcohol and interpretation of fatal blood concentrations." Hum Toxicol 2 (1983): 5-14
  5. Seixas FA "Drug/alcohol interactions: avert potential dangers." Geriatrics 34 (1979): 89-102
View all 5 references

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Moderate

aspirin food

Applies to: aspirin / butalbital

GENERALLY AVOID: The concurrent use of aspirin or nonsteroidal anti-inflammatory drugs (NSAIDs) and ethanol may lead to gastrointestinal (GI) blood loss. The mechanism may be due to a combined local effect as well as inhibition of prostaglandins leading to decreased integrity of the GI lining.

MANAGEMENT: Patients should be counseled on this potential interaction and advised to refrain from alcohol consumption while taking aspirin or NSAIDs.

References

  1. "Product Information. Motrin (ibuprofen)." Pharmacia and Upjohn PROD (2002):

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Minor

tenofovir food

Applies to: emtricitabine / nelfinavir / tenofovir

Food enhances the oral absorption and bioavailability of tenofovir, the active entity of tenofovir disoproxil fumarate. According to the product labeling, administration of the drug following a high-fat meal increased the mean peak plasma concentration (Cmax) and area under the concentration-time curve (AUC) of tenofovir by approximately 14% and 40%, respectively, compared to administration in the fasting state. However, administration with a light meal did not significantly affect the pharmacokinetics of tenofovir compared to administration in the fasting state. Food delays the time to reach tenofovir Cmax by approximately 1 hour. Tenofovir disoproxil fumarate may be administered without regard to meals.

References

  1. "Product Information. Viread (tenofovir)." Gilead Sciences (2001):

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Minor

aspirin food

Applies to: aspirin / butalbital

One study has reported that coadministration of caffeine and aspirin lead to a 25% increase in the rate of appearance and 17% increase in maximum concentration of salicylate in the plasma. A significantly higher area under the plasma concentration time curve of salicylate was also reported when both drugs were administered together. The exact mechanism of this interaction has not been specified. Physicians and patients should be aware that coadministration of aspirin and caffeine may lead to higher salicylate levels faster.

References

  1. Yoovathaworn KC, Sriwatanakul K, Thithapandha A "Influence of caffeine on aspirin pharmacokinetics." Eur J Drug Metab Pharmacokinet 11 (1986): 71-6

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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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