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fosphenytoin injection

Theophyllines/Hydantoins (mono deleted 03/26/2014)

This information is generalized and not intended as specific medical advice. Consult your healthcare professional before taking or discontinuing any drug or commencing any course of treatment.

Medical warning:

Moderate. These medicines may cause some risk when taken together. Contact your healthcare professional (e.g. doctor or pharmacist) for more information.

How the interaction occurs:

When these two medicines are taken together, the effects of one or both medicines may decrease.

What might happen:

A decrease in the beneficial effects of one or both medicines may occur.

What you should do about this interaction:

If you experience difficulty breathing or your seizure control changes, contact your doctor. It may be necessary to adjust the dose of your medicines.Your healthcare professionals (e.g. doctor or pharmacist) may already be aware of this drug interaction and may be monitoring you for it. Do not start, stop, or change the dosage of any medicine before checking with them first.


1.Taylor JW, Hendeles LWeinberger M, Lyon LW, Wyatt R, Riegelman S. The interaction of phenytoin and theophylline. Drug Intell Clin Pharm 1980; 14(9):638.
2.Marquis JF, Carruthers SG, Spence JD, Brownstone YS, Toogood JH. Phenytoin-theophylline interaction. N Engl J Med 1982 Nov 4; 307(19):1189-90.
3.Anonymous. Phenytoin-theophylline-quinidine interactions. N Engl J Med 1983 Mar 24;308(12):724-5.
4.Miller M, Cosgriff J, Kwong T, Morken DA. Influence of phenytoin on theophylline clearance. Clin Pharmacol Ther 1984 May;35(5):666-9.
5.Sklar SJ, Wagner JC. Enhanced theophylline clearance secondary to phenytoin therapy. Drug Intell Clin Pharm 1985 Jan;19(1):34-6.
6.Crowley JJ, Cusack BJ, Jue SG, Koup JR, Park BK, Vestal RE. Aging and drug interactions. II. Effect of phenytoin and smoking on the oxidation of theophylline and cortisol in healthy men. J Pharmacol Exp Ther 1988 May; 245(2):513-23.
7.Adebayo GI. Interaction between phenytoin and theophylline in healthy volunteers. Clin Exp Pharmacol Physiol 1988 Nov;15(11):883-7.
8.Landsberg K, Shalansky S. Interaction between phenytoin and theophylline. Can J Hosp Pharm 1988 Feb;41(1):31-2.
9.Nicholson JP, Basile SA, Cury JD. Massive theophylline dosing in a heavy smoker receiving both phenytoin and phenobarbital. Ann Pharmacother 1992 Mar;26(3):334-6.

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