Primidone Carbamazepine

Anticonvulsants (barbiturates, including phenobar-bital and primidone carbamazepine felbamate phenytoin topiramate vigabatrin)... 

Antiepileptic drugs (ethosuc- Spherisorb ODS-1, 3 pm cinimide, primidon, carbamazepine-10,11 -diol, carbamazepine-10,11-epoxide, carbamazepine, phenytoin... 

Phenobarbital Phenytoin Primidone Carbamazepine Reduced effect of carbamazepine usually compensated by the action of the added drug risk of carbamazepine toxicity when interfering drug is withdrawn Induction of carbamazepine metabolism... 

Primary, commonly used antiepileptics include phenytoin, phenobarbital, primidone, carbamazepine, ethosuximide and valproic acid. In addition, two benzodiazepines, diazepam and... 

Bourgeois BF, Dodson WE, FerrendeUi JA. Interactions between primidone, carbamazepine, and nicotinamide. Neurology p982) 32,1122-26. 

Benetello P, Furlanut M. Primidone-carbamazepine interaction cUnical consequences. IntJ Clin Pharmacol Res ( 9S7) 7, 165-8. 

Antiepileptics Barbiturates (e.g. phenobarbital, primidone), Carbamazepine, Phenytoin, Topiramate... 

Gas Chromatographic Determination of Phenytoin, Phenobarbitone, Primidone, Carbamazepine, and Pheneturide (or Acetylpheneturide) from the Same SeriDn Specimen... 

Detection and result The chromatogram was freed from mobile phase (first dried for 5 min in a stream of cold air, then heated for 10 min at 110°C and allowed to cool), immersed for 5 s in the reagent solution and finally heated for 2 min at 110°C. Grey to grey-blue zones were formed on a light background. The following hRf values were obtained primidone QiR( 10-15) carbamazepine hRf 40 — 45) phenytoin hR( 50 — 55) phenobarbital hRf 60) ethosuximide hRf 75) hexobarbital hRf 90 — 95). 

Fig. 1 Reflectance scan of a blank (A) and of a mixture of antiepileptics with 500 ng substance per chromatogram zone (B). Start (1), primidone (2), carbamazepine (3), phenytoin (4), phenobarbital (5), ethosuximide (6), hexobarbital (7) and solvent front (8).

When carbamazepine is administered with primidone, decreased primidone levels and higher carbamazepine serum levels may result. Cimetidine administered with carbamazepine may result in an increase in plasma levels of carbamazepine that can lead to toxicity. Blood levels of lamotrigine increase when the agent is administered with valproic acid, requiring a lower dosage of lamotrigine... 

Commonly used drugs that induce liver enzymes (rifampin, phenytoin, carbamazepine, barbiturates, primidone, topiramate) and reduce efficacy of CHC... 

Phenobarbital, phenytoin, primidone, and carbamazepine are potent inducers of cytochrome P450 (CYP450), epoxide hydrolase, and uridine diphosphate glucuronosyltransferase enzyme systems. Valproic acid inhibits many hepatic enzyme systems and displaces some drugs from plasma albumin. 

While regular monitoring of plasma phenytoin levels can result in improved seizure control, the benefit derived from measuring other commonly prescribed anticonvulsant drugs is difficult to assess. Phenobarbitone, primidone, and carbamazepine will be discussed briefly. 

T4. Toseland, P. A., Grove, J., and Berry, D. J., An isothermal GLC determination of the plasma levels of carbamazepine, diphenylhydantoin, phenobarbitone and primidone. Clin. Chim. Acta 38, 321-328 (1972). 

From the clinical point of view, antiepileptic drugs are primarily divided into two categories those effective in treating major attacks (phenytoin, carbamazepine, mephobarbi-tal, and also primidone), and those effective in treating minor attacks (ethosuximide, acetazolamide, clonazepam, trimethadione, and valproic acid). 

From the chemical point of view, formally, antiepileptic drugs could be classified as derivatives of hydantoins (phenytoin, mephenytoin, ethotoin), barbiturates (phenobarbital, mephobarbital, and primidone), succinimides (ethosuximide, methosuximide, phensux-imide), benzodiazepines (diazepam, chlorodiazepoxide, clonazepam, lorazepam), oxazo-lidines (trimethadione, paramethadione), and also valproic acid, carbamazepine, and acetazolamide. 

Epilepsy, monotherapy Indicated for conversion to monotherapy in adults with partial seizures who are receiving treatment with carbamazepine, phenytoin, phenobarbital, primidone, or valproate as the single antiepileptic drug (AED). 

The apparent clearance of lamotrigine is affected by the coadministration of AEDs. Lamotrigine is eliminated more rapidly in patients who have been taking hepatic enzyme inducing antiepileptic drugs (ElAEDs), including carbamazepine, phenytoin, phenobarbital, and primidone. 

Lamotrigine Added to Carbamazepine, Phenytoin, Phenobarbital, or Primidone (Without Valproic Acid) in Patients >12 Years of Age ... 

Discontinuing carbamazepine, phenytoin, phenobarbital, or primidone should prolong the half-life of lamotrigine discontinuing valproate should shorten the half-life of lamotrigine. 

Stopping oral contraceptives - For women not taking carbamazepine, phenytoin, phenobarbital, primidone, or rifampin, the maintenance dose of lamotrigine may need to be decreased by as much as 50% of the maintenance dose with concurrent oral contraceptives. 

Drugs that may affect lamotrigine include acetaminophen, carbamazepine, folate inhibitors, oral contraceptives, phenobarbital, phenytoin, primidone, rifamycins, succinimides, and valproic acid. 

Drugs that may affect primidone include acetazolamide, carbamazepine, hydantoins, isoniazid, nicotinamide, and succinimides. 

Drugs that may be affected by primidone include carbamazepine. 

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