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Drug Interactions between Dilantin and doxepin

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

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Interactions between your drugs

Moderate

phenytoin doxepin

Applies to: Dilantin (phenytoin) and doxepin

MONITOR: Tricyclic antidepressants may increase serum phenytoin levels. In vitro studies suggest the mechanism may involve inhibition of CYP450 2C19-catalyzed phenytoin p-hydroxylation by tricyclic antidepressants, especially imipramine and amitriptyline. Phenytoin may induce the hepatic metabolism of desipramine resulting in decreased plasma concentrations. In addition, tricyclic antidepressants may lower the seizure threshold.

MANAGEMENT: Clinical monitoring of patient response, tolerance, and serum phenytoin concentrations is recommended. Patients should be advised to notify their doctor if they experience loss of seizure control or symptoms of phenytoin toxicity (drowsiness, visual disturbances, change in mental status, nausea, or ataxia). Phenytoin dosage may need to be adjusted.

References

  1. Fogel BS, Haltzman S "Desipramine and phenytoin: a potential drug interaction of therapeutic relevance." J Clin Psychiatry 48 (1987): 387-8
  2. Houghton GW, Richens A "Inhibition of phenytoin metabolism by other drugs used in epilepsy." Int J Clin Pharmacol 12 (1975): 210-6
  3. Perucca E, Richens A "Interaction between phenytoin and imipramine." Br J Clin Pharmacol 4 (1977): 485-6
  4. Shin JG, Park JY, Kim MJ, et al. "Inhibitory effects of tricyclic antidepressants (TCAs) on human cytochrome P450 enzymes in vitro: mechanism of drug interaction between TCAs and phenytoin." Drug Metab Dispos 30 (2002): 1102-7
  5. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  6. Cerner Multum, Inc. "Australian Product Information." O 0
  7. Agencia Española de Medicamentos y Productos Sanitarios Healthcare "Centro de información online de medicamentos de la AEMPS - CIMA. https://cima.aemps.es/cima/publico/home.html" (2008):
  8. Cerner Multum, Inc. "Canadian Product Information." O 0 (2015):
  9. Cerner Multum, Inc "ANVISA Bulário Eletrônico." O 0 (2015):
View all 9 references

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Drug and food interactions

Moderate

phenytoin food

Applies to: Dilantin (phenytoin)

ADJUST DOSING INTERVAL: Phenytoin bioavailability may decrease to subtherapeutic levels when the suspension is given concomitantly with enteral feedings. The mechanism may be related to phenytoin binding to substances in the enteral formula (e.g., calcium, protein) and/or binding to the tube lumen. Data have been conflicting and some studies have reported no changes in phenytoin levels, while others have reported significant reductions.

MONITOR: Acute consumption of alcohol may increase plasma phenytoin levels. Chronic consumption of alcohol may decrease plasma phenytoin levels. The mechanism of this interaction is related to induction of phenytoin metabolism by ethanol during chronic administration. Other hydantoin derivatives may be similarly affected by ethanol.

MANAGEMENT: Some experts have recommended interrupting the feeding for 2 hours before and after the phenytoin dose, giving the phenytoin suspension diluted in water, and flushing the tube with water after administration; however, this method may not entirely avoid the interaction and is not always clinically feasible. Patients should be closely monitored for clinical and laboratory evidence of altered phenytoin efficacy and levels upon initiation and discontinuation of enteral feedings. Dosage adjustments or intravenous administration may be required until therapeutic serum levels are obtained. In addition, patients receiving phenytoin therapy should be warned about the interaction between phenytoin and ethanol and they should be advised to notify their physician if they experience worsening of seizure control or symptoms of toxicity, including drowsiness, visual disturbances, change in mental status, nausea, or ataxia.

References

  1. Sandor P, Sellers EM, Dumbrell M, Khouw V "Effect of short- and long-term alcohol use on phenytoin kinetics in chronic alcoholics." Clin Pharmacol Ther 30 (1981): 390-7
  2. Holtz L, Milton J, Sturek JK "Compatibility of medications with enteral feedings." JPEN J Parenter Enteral Nutr 11 (1987): 183-6
  3. Sellers EM, Holloway MR "Drug kinetics and alcohol ingestion." Clin Pharmacokinet 3 (1978): 440-52
  4. "Product Information. Dilantin (phenytoin)." Parke-Davis PROD (2001):
  5. Doak KK, Haas CE, Dunnigan KJ, et al. "Bioavailability of phenytoin acid and phenytoin sodium with enteral feedings." Pharmacotherapy 18 (1998): 637-45
  6. Rodman DP, Stevenson TL, Ray TR "Phenytoin malabsorption after jejunostomy tube delivery." Pharmacotherapy 15 (1995): 801-5
  7. Au Yeung SC, Ensom MH "Phenytoin and enteral feedings: does evidence support an interaction?" Ann Pharmacother 34 (2000): 896-905
  8. Ozuna J, Friel P "Effect of enteral tube feeding on serum phenytoin levels." J Neurosurg Nurs 16 (1984): 289-91
  9. Faraji B, Yu PP "Serum phenytoin levels of patients on gastrostomy tube feeding." J Neurosci Nurs 30 (1998): 55-9
  10. Marvel ME, Bertino JS "Comparative effects of an elemental and a complex enteral feeding formulation on the absorption of phenytoin suspension." JPEN J Parenter Enteral Nutr 15 (1991): 316-8
  11. Fleisher D, Sheth N, Kou JH "Phenytoin interaction with enteral feedings administered through nasogastric tubes." JPEN J Parenter Enteral Nutr 14 (1990): 513-6
  12. Haley CJ, Nelson J "Phenytoin-enteral feeding interaction." DICP 23 (1989): 796-8
  13. Guidry JR, Eastwood TF, Curry SC "Phenytoin absorption in volunteers receiving selected enteral feedings." West J Med 150 (1989): 659-61
  14. Krueger KA, Garnett WR, Comstock TJ, Fitzsimmons WE, Karnes HT, Pellock JM "Effect of two administration schedules of an enteral nutrient formula on phenytoin bioavailability." Epilepsia 28 (1987): 706-12
  15. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  16. Cerner Multum, Inc. "Australian Product Information." O 0
View all 16 references

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Moderate

doxepin food

Applies to: doxepin

GENERALLY AVOID: Concomitant use of ethanol and a tricyclic antidepressant (TCA) may result altered TCA plasma levels and efficacy, and additive impairment of motor skills, especially driving skills. Acute ethanol ingestion may inhibit TCA metabolism, while chronic ingestion of large amounts of ethanol may induce hepatic TCA metabolism.

MANAGEMENT: Patients should be advised to avoid alcohol during TCA therapy. Alcoholics who have undergone detoxification should be monitored for decreased TCA efficacy. Dosage adjustments may be required.

References

  1. Dorian P, Sellers EM, Reed KL, et al. "Amitriptyline and ethanol: pharmacokinetic and pharmacodynamic interaction." Eur J Clin Pharmacol 25 (1983): 325-31
  2. Warrington SJ, Ankier SI, Turner P "Evaluation of possible interactions between ethanol and trazodone or amitriptyline." Neuropsychobiology 15 (1986): 31-7
  3. Sandoz M, Vandel S, Vandel B, Bonin B, Allers G, Volmat R "Biotransformation of amitriptyline in alcoholic depressive patients." Eur J Clin Pharmacol 24 (1983): 615-21
  4. Ciraulo DA, Barnhill JG, Jaffe JH "Clinical pharmacokinetics of imipramine and desipramine in alcoholics and normal volunteers." Clin Pharmacol Ther 43 (1988): 509-18
  5. Seppala T, Linnoila M, Elonen E, Mattila MJ, Makl M "Effect of tricyclic antidepressants and alcohol on psychomotor skills related to driving." Clin Pharmacol Ther 17 (1975): 515-22
  6. Ciraulo DA, Barnhill JG, Jaffe JH, Ciraulo AM, Tarmey MF "Intravenous pharmacokinetics of 2-hydroxyimipramine in alcoholics and normal controls." J Stud Alcohol 51 (1990): 366-72
  7. Ciraulo DA, Alderson LM, Chapron DJ, Jaffe JH, Subbarao B, Kramer PA "Imipramine disposition in alcoholics." J Clin Psychopharmacol 2 (1982): 2-7
View all 7 references

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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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