Hydantoins/Folic Acid; Pyrimethamine Interactions
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.
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, folic acid and pyrimethamine may cause your body to not process the hydantoin (e.g. phenytoin) properly.
What might happen:
Your blood level of the hydantoin may decrease which may cause an increased chance of seizures.
What you should do about this interaction:
The blood level of your hydantoin may need to be monitored more often. The dose of your hydantoin may need to be adjusted.Your healthcare professionals (e.g. doctor or pharmacist) may already be aware of this 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.Kutt H, Winters W, McDowell FH. Depression of prahydroxylation of diphenylhydantoin by antituberculosis chemotherapy. Neurology 1966 Jun; 16(6):594-602.
- 2.Reynolds EH. Effects of folic acid on the mental state and fit-frequency of drug- treated epileptic patients. Lancet 1967 May 20;1(7499):1086-8.
- 3.Olesen OV, Jensen ON. The influence of folic acid on phenytoin (DPH) metabolism and the 24- hours fluctuation in urinary output of 5-(p-hydroxyphenyl)-5 phenyl- hydantoin (HPPH). Acta Pharmacol Toxicol (Copenh) 1970;28(4):265-9.
- 4.Jensen ON, Olesen OV. Subnormal serum folate due to anticonvulsive therapy. A double-blind study of the effect of folic acid treatment in patients with drug- induced subnormal serum folates. Arch Neurol 1970 Feb; 22(2):181-2.
- 5.Baylis EM, Crowley JM, Preece JM, Sylvester PE, Marks V. Influence of folic acid on blood-phenytoin levels. Lancet 1971 Jan 9;1(7689):62-4.
- 6.Mattson RH, Gallagher BB, Reynolds EH, Glass D. Folate therapy in epilepsy. A controlled study. Arch Neurol 1973 Aug;29(2):78-81.
- 7.Furlanut M, Benetello P, Avogaro A, Dainese R. Effects of folic acid on phenytoin kinetics in healthy subjects. Clin Pharmacol Ther 1978 Sep; 24(3):294-7.
- 8.Gibberd FB, Nicholls A, Wright MG. The influence of folic acid on the frequency of epileptic attacks. Eur J Clin Pharmacol 1981 Jan;19(1):57-60.
- 9.Inoue F. Clinical implications of anticonvulsant-induced folate deficiency. Clin Pharm 1982 Jul-Aug;1(4):372-3.
- 10.MacCosbe PE, Toomey K. Interaction of phenytoin and folic acid. Clin Pharm 1983 Jul-Aug;2(4):362-9.
- 11.Berg MJ, Fischer LJ, Rivey MP, Vern BA, Lantz RK, Schottelius DD. Phenytoin and folic acid interaction: a preliminary report. Ther Drug Monit 1983;5(4):389-94.
- 12.Berg MJ, Rivey MP, Vern BA, Fischer LJ, Schottelius DD. Phenytoin and folic acid: individualized drug-drug interaction. Ther Drug Monit 1983; 5(4):395-9.
- 13.Yuen GJ. Interaction of phenytoin and folic acid: an alternative explanation. Clin Pharm 1984 Mar-Apr;3(2):116, 119.
- 14.Rivey MP, Schottelius DD, Berg MJ. Phenytoin-folic acid: a review. Drug Intell Clin Pharm 1984 Apr;18(4):292-301.
- 15.Berg MJ, Fincham RW, Ebert BE, Schottelius DD. Phenytoin pharmacokinetics: before and after folic acid administration. Epilepsia 1992 Jul-Aug;33(4):712-20.
CONDITIONS OF USE: The information in this database is intended to supplement, not substitute for, the expertise and judgment of healthcare professionals. The information is not intended to cover all possible uses, directions, precautions, drug interactions or adverse effects, nor should it be construed to indicate that use of a particular drug is safe, appropriate or effective for you or anyone else. A healthcare professional should be consulted before taking any drug, changing any diet or commencing or discontinuing any course of treatment.