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Drug Interaction Report

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

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Interactions between your drugs

Moderate

PHENobarbital aminophylline

Applies to: aminophylline / ephedrine / phenobarbital / potassium iodide, aminophylline / ephedrine / phenobarbital / potassium iodide

MONITOR: Barbiturates may decrease serum levels and therapeutic effects of the methylxanthines. The mechanism is barbiturate induction of CYP450 3A4 and 1A2 hepatic metabolism of methylxanthines.

MANAGEMENT: Close observation for clinical and laboratory evidence of decreased methylxanthine effect is indicated if these drugs must be used together. Patients should be advised to notify their physician if they experience a worsening of their respiratory symptoms.

References

  1. Upton RA (1991) "Pharmacokinetic interactions between theophylline and other medication (Part I)." Clin Pharmacokinet, 20, p. 66-80
  2. Bukowskyj M, Nakatsu K, Munt PW (1984) "Theophylline reassessed." Ann Intern Med, 101, p. 63-73
  3. Landay RA, Gonzalez MA, Taylor JC (1978) "Effect of phenobarbital on theophylline disposition." J Allergy Clin Immunol, 62, p. 27-9
  4. Dahlqvist R, Steiner E, Koike Y, von Bahr C, Lind M, Billing B (1989) "Induction of theophylline metabolism by pentobarbital." Ther Drug Monit, 11, p. 408-10
View all 4 references

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Moderate

PHENobarbital tipranavir

Applies to: aminophylline / ephedrine / phenobarbital / potassium iodide, tipranavir

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 Antiretroviral response should be monitored more closely whenever a CYP450 3A4 inducer is added to or withdrawn from therapy, and the antiretroviral regimen adjusted as necessary.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. (2001) "Product Information. Invirase (saquinavir)." Roche Laboratories
  2. (2001) "Product Information. Crixivan (indinavir)." Merck & Co., Inc
  3. (2001) "Product Information. Viracept (nelfinavir)." Agouron Pharma Inc
  4. Brooks J, Daily J, Schwamm L (1997) "Protease inhibitors and anticonvulsants." AIDS Clin Care, 9, 87,90
  5. Barry M, Gibbons S, Back D, Mulcahy F (1997) "Protease inhibitors in patients with HIV disease. Clinically important pharmacokinetic considerations." Clin Pharmacokinet, 32, p. 194-209
  6. (2001) "Product Information. Agenerase (amprenavir)." Glaxo Wellcome
  7. Acosta EP, Henry K, Baken L, Page LM, Fletcher CV (1999) "Indinavir concentrations and antiviral effect." Pharmacotherapy, 19, p. 708-12
  8. Sommadossi JP (1999) "HIV protease inhibitors: pharmacologic and metabolic distinctions." AIDS, 13, s29-40
  9. Hugen PWH, Burger DM, Brinkman K, terHofstede HJM, Schuurman R, Koopmans PP, Hekster YA (2000) "Carbamazepine-indinavir interaction causes antiretroviral therapy failure." Ann Pharmacother, 34, p. 465-70
  10. Durant J, Clevenbergh P, Garraffo R, Halfon P, Icard S, DelGiudice P, Montagne N, Schapiro JM, Dellamonica P (2000) "Importance of protease inhibitor plasma levels in HIV-infected patients treated with genotypic-guided therapy: pharmacological data from the Viradapt Study." Aids, 14, p. 1333-9
  11. (2001) "Product Information. Fortovase (saquinavir)." Roche Laboratories
  12. (2003) "Product Information. Reyataz (atazanavir)." Bristol-Myers Squibb
  13. (2003) "Product Information. Lexiva (fosamprenavir)." GlaxoSmithKline
  14. Liedtke MD, Lockhart SM, Rathbun RC (2004) "Anticonvulsant and antiretroviral interactions." Ann Pharmacother, 38, p. 482-9
  15. (2005) "Product Information. Aptivus (tipranavir)." Boehringer-Ingelheim
  16. (2006) "Product Information. Prezista (darunavir)." Ortho Biotech Inc
  17. Canadian Pharmacists Association (2006) e-CPS. http://www.pharmacists.ca/function/Subscriptions/ecps.cfm?link=eCPS_quikLink
View all 17 references

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Minor

ePHEDrine aminophylline

Applies to: aminophylline / ephedrine / phenobarbital / potassium iodide, aminophylline / ephedrine / phenobarbital / potassium iodide

Ephedrine-methylxanthine combinations are used for the treatment of asthma but the efficacy of the combination has been questioned. This combination may lead to increased xanthine side effects. The mechanism is unknown, but may be related to synergistic pharmacologic effects. Patients using this combination should be closely monitored for side effects such as nausea, vomiting, tachycardia, nervousness, or insomnia. If side effects are noted, the dosage of the xanthine may need to be decreased.

References

  1. Weinberger M, Bronsky E, Bensch GW, Bock GN, Yecies JJ (1975) "Interaction of ephedrine and theophylline." Clin Pharmacol Ther, 17, p. 585-92
  2. Sims JA, doPico GA, Reed CE (1978) "Bronchodilating effect of oral theophylline-ephedrine combination." J Allergy Clin Immunol, 62, p. 15-21
  3. Tinkelman DG, Avner SE (1977) "Ephedrine therapy in asthmatic children. Clinical tolerance and absence of side effects." JAMA, 237, p. 553-7
  4. Weinberger MM, Brousky EA (1974) "Evaluation of oral bronchodilator therapy in asthmatic children: bronchodilators in asthmatic children." J Pediatr, 84, p. 421-7
  5. Badiei B, Faciane J, Sly M (1975) "Effect of throphylline, ephedrine and theri combination upon exercise-induced airway obstruction." Ann Allergy, 35, p. 32-6
View all 5 references

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Drug and food interactions

Major

PHENobarbital food

Applies to: aminophylline / ephedrine / phenobarbital / potassium iodide

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

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Moderate

tipranavir food

Applies to: tipranavir

ADJUST DOSING INTERVAL: Food does not appear to substantially alter the pharmacokinetics of tipranavir. When tipranavir capsules or oral solution was coadministered with ritonavir capsules at steady-state, no clinically significant changes in tipranavir peak plasma concentration (Cmax) and systemic exposure (AUC) were observed under fed conditions (500 to 682 kcal, 23% to 25% calories from fat) relative to fasted conditions. The effect of food on tipranavir exposure during coadministration with ritonavir tablets has not been evaluated. High-fat foods may enhance the gastrointestinal absorption of tipranavir. In a multiple-dose study, administration of tipranavir capsules with a high-fat meal (868 kcal, 53% from fat, 31% from carbohydrates) increased the oral bioavailability of tipranavir by 31% compared to administration with toast and skimmed milk, but did not significantly affect tipranavir Cmax. Thus, tipranavir may be safely taken with standard or high-fat meals.

MANAGEMENT: Tipranavir coadministered with low-dose ritonavir should be taken with food to improve the gastrointestinal tolerability of ritonavir. According to the product labeling, tipranavir coadministered with ritonavir capsules or solution can be taken with or without meals, whereas tipranavir coadministered with ritonavir tablets must be taken with meals.

References

  1. (2005) "Product Information. Aptivus (tipranavir)." Boehringer-Ingelheim
  2. Cerner Multum, Inc. "UK Summary of Product Characteristics."
  3. Canadian Pharmacists Association (2006) e-CPS. http://www.pharmacists.ca/function/Subscriptions/ecps.cfm?link=eCPS_quikLink
  4. Cerner Multum, Inc. "Australian Product Information."
View all 4 references

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Moderate

ePHEDrine food

Applies to: aminophylline / ephedrine / phenobarbital / potassium iodide

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

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Moderate

aminophylline food

Applies to: aminophylline / ephedrine / phenobarbital / potassium iodide

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

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Therapeutic duplication warnings

No duplication 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.

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Further information

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