with Vitamin B12 (Cobalamin)|
In one study, 27 patients aged 15 to 54 treated with phenobarbitone (90
mg/day phenobarbital) and diphenylhydantion (300 mg/day phenytoin) regularly for
3 to 32 years had serum levels of vitamin B6 and B12 that were increased
significantly relative to controls (Dastur and Dave 1987). Increased vitamin B12
levels in serum may indicate hepatic damage from anticonvulsants and reflect an
impairment in hepatic storage capacity for the vitamin. Studies in rats suggest
that phenytoin sodium may reduce vitamin B12 uptake by certain cells, including
hematopoietic and neural cells (Latham et al. 1990). It is not known if
phenytoin depletes vitamin B12 levels.
In one study, the bioavailability of tetracycline hydrochloride was reduced
significantly by concomitant administration of vitamin B complex to healthy
subjects (Omray 1981). Patients should be cautioned to take vitamin B complex
supplements at different times from tetracycline.
Dastur D, Dave U. Effect of prolonged anticonvulsant medication in epileptic
patients: serum lipids, vitamins B6, B12 and folic acid,
proteins and fine structure of liver. Epilepsia. 1987;28:147-159.
Latham J, Gill DS, Wickramasinghe SN. Effects of phenytoin sodium on doubling
time, deoxyuridine suppression, 3H-methotrexate uptake and 57C0-cyanocobalamin
uptake in HL60 cells. Clin Lab Haematol. 1990;12(1):67-75.
Omray A. Evaluation of pharmacokinetic parameters of tetracylcine
hydrochloride upon oral administration with vitamin C and vitamin B complex.
Hindustan Antibiot Bull.
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