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Drug Interactions between atazanavir / cobicistat and Phenaz Plus

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

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Interactions between your drugs

Moderate

butabarbital atazanavir

Applies to: Phenaz Plus (butabarbital / hyoscyamine / phenazopyridine) and atazanavir / cobicistat

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 Antiretroviral response should be monitored more closely whenever a CYP450 3A4 inducer is added to or withdrawn from therapy, and the antiretroviral regimen adjusted as necessary.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

butabarbital food

Applies to: Phenaz Plus (butabarbital / hyoscyamine / phenazopyridine)

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

atazanavir food

Applies to: atazanavir / cobicistat

ADJUST DOSING INTERVAL: Administration of atazanavir with food enhances oral bioavailability and reduces pharmacokinetic variability. According to the manufacturer, administration with a light meal increased the peak plasma concentration (Cmax) and area under the concentration-time curve (AUC) of a single 400 mg dose of atazanavir by 57% and 70%, respectively, relative to the fasting state. Administration with a high-fat meal resulted in a mean increase of 35% in atazanavir AUC and no change in Cmax compared to fasting. The coefficient of variation of AUC and Cmax decreased by approximately one-half when given with either a light or high-fat meal compared to the fasting state.

MANAGEMENT: To ensure maximal oral absorption, atazanavir should be administered with or immediately after a meal.

References

  1. "Product Information. Reyataz (atazanavir)." Bristol-Myers Squibb (2003):

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Moderate

hyoscyamine food

Applies to: Phenaz Plus (butabarbital / hyoscyamine / phenazopyridine)

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 "Drug effects on psychomotor skills related to driving: interaction of atropine, glycopyrrhonium and alcohol." Eur J Clin Pharmacol 6 (1973): 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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