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Drug Interactions between Di-Phen and sodium oxybate

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

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Major

phenytoin sodium oxybate

Applies to: Di-Phen (phenytoin) and sodium oxybate

GENERALLY AVOID: The central nervous system and respiratory depressant effects of sodium oxybate, which is the sodium salt of gamma hydroxybutyrate (GHB), may be potentiated by concomitant use of other agents with CNS depressant effects including anticonvulsants. An increased risk of serious adverse reactions such as respiratory depression, hypotension, profound sedation, syncope, coma, and even death should be considered.

ADJUST DOSE: Animal data suggest a possible pharmacokinetic interaction between sodium oxybate and certain anticonvulsants like valproate, phenytoin, ethosuximide, and trimethadione that can inhibit the enzyme GHB dehydrogenase, which converts GHB to succinic semialdehyde. In humans, coadministration of sodium oxybate (6 gm/day in two equal doses 4 hours apart) with divalproex sodium (1250 mg valproic acid per day) has been associated with a 25% mean increase in systemic exposure to sodium oxybate and a greater impairment on some tests of attention and working memory. Pharmacokinetic data are not available for other anticonvulsants.

MANAGEMENT: Concomitant use of sodium oxybate with other CNS depressants should be avoided whenever possible. Otherwise, close monitoring and/or dosage reductions should be considered. For patients already stabilized on sodium oxybate who are prescribed divalproex sodium, the manufacturer recommends that the nightly dosage of sodium oxybate be reduced initially by at least 20%. Conversely, for patients already taking divalproex sodium, it is recommended that prescribers use a lower starting dosage of sodium oxybate upon initiation of treatment. Further dosage adjustments should be made according to patient response and tolerance. No specific dosage recommendations are available for use with other anticonvulsants. All patients treated with sodium oxybate should be advised not to drive, operate machinery, or engage in hazardous activities requiring mental alertness and motor coordination for at least 6 hours after taking the second nightly dose of sodium oxybate and until they know how the medication affects them.

References

  1. (2002) "Product Information. Xyrem (sodium oxybate)." Orphan Medical
  2. Cerner Multum, Inc. "UK Summary of Product Characteristics."
  3. (2020) "Product Information. Xywav (calcium/magnesium/potass/sodium oxybates)." Jazz Pharmaceuticals

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Drug and food interactions

Major

sodium oxybate food

Applies to: sodium oxybate

CONTRAINDICATED: Alcohol may potentiate the central nervous system and respiratory depressant effects of sodium oxybate, which is the sodium salt of gamma hydroxybutyrate (GHB). An increased risk of serious adverse reactions such as respiratory depression, hypotension, profound sedation, syncope, coma, and even death should be anticipated.

ADJUST DOSING INTERVAL: Food may delay the absorption and significantly decrease the bioavailability of sodium oxybate. When sodium oxybate was administered immediately after a high-fat meal, the time to reach peak plasma concentration (Tmax) increased from 0.75 hour to 2 hours, the peak plasma concentration (Cmax) decreased by a mean of 59%, and the systemic exposure (AUC) decreased by a mean of 37%.

MANAGEMENT: The concomitant use of sodium oxybate with alcohol is considered contraindicated. The first dose of sodium oxybate should be taken at least 2 hours after a meal to ensure maximal absorption.

References

  1. (2002) "Product Information. Xyrem (sodium oxybate)." Orphan Medical

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Moderate

phenytoin food

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

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