Phenytoins

Therapeutic Function Antiepileptic Chemical Name 5,5-diphenyl-2,4-imidazolidinedione Common Name Diphenylhydantoin Structural Formula h 

Trade Name Manufacturer Country Year Introduced 

10 g of benzophenone (1 mol), 4 g of potassium cyanide (1.22 mols) and 16 g of ammonium carbonate (3.3 mols) are dissolved in 100 cc of 60% (by volume) ethyl alcohol and the mixture warmed under a reflux condenser without stirring at 58° to 62°C. After warming the mixture for 10 hours a partial vacuum is applied and the temperature Is raised enough to permit concentration of the reaction mixture to two-thirds of its initial volume. 

A slight excess of mineral acid, such as sulfuric or hydrochloric acid is added to acidify the mixture which is then chilled and the solid which separates is filtered off. It is then treated with an aqueous solution of dilute sodium hydroxide to dissolve the hydantoin from the solid unreacted benzophenone. After filtration, the alkaline extract is then acidified to cause the separation of solid pure diphenylhydantoin which is filtered off and dried. It melts at 293° to 296°C. 

A net yield of about 95% Is obtained by the procedure described above. If the time of warming the reaction mixture is increased three- or four-fold, practically 100% net yields are obtained. The same high net yields are also obtained by heating for even longer periods of time. For example, by heating for 90 hours, a 100% net yield, or 67% gross yield, is obtained. 

Patent 2,409,754 October 22,1946 assigned to Parke, Davis Company 

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Cj jH,2N202. Used as its sodium salt, which is a white hygroscopic powder. Unstable, readily absorbing carbon dioxide and liberating phenytoin. Made by treating a-bromodi-phenylacetylurea with alcoholic ammonia. It has a mild hypnotic and strong anticonvulsant action, and is used in the treatment of grand-mal and focal epilepsy. 

Similarly, hydantoins can be arylated at N-3. For example, treatment of 5,5-diphenyIhydantoin (4), R = R = Cg (phenytoin), with -tolyUead triacetate in the presence of sodium hydride and a catalytic amount of copper(II) acetate (37) gives compound (7). 

The oxa2ohdinedione trimethadione [127-48-0] C H NO (50), at one time the dmg of choice for the treatment of absence sei2ures, has been replaced by ethosuximide (41) and valproate (49). (50) has a distinct profile from that of phenytoin but causes photophobia and night blindness in approximately 30% of the patients taking it and has the CNS and sedative properties seen for other anticonvulsants together with moderate neutropenia, hepatitis, and skin rashes (13). Trimethadione does not appear to produce its effects via modulation of GABA-mediated responses. 

Phenytoin. Phenytoin sodium is sodium diphenylhydantoin [630-93-3] which is stmcturally related to the barbiturates. It was originally introduced as an anticonvulsant (18) (see Hypnotics, sedatives, and anticonvulsants) and later found to have antiarrhythmic properties (19), although not approved by the PDA for any arrhythmic indications. Phenytoin is effective in the treatment of ventricular arrhythmias associated with acute MI and with digitalis toxicity (20). It is not very effective in treatment of supraventricular arrhythmias (20). 

Phenytoin s absorption is slow and variable yet almost complete absorption eventually occurs after po dosing. More than 90% of the dmg is bound to plasma protein. Peak plasma concentrations are achieved in 1.5—3 h. Therapeutic plasma concentrations are 10—20 lg/mL but using fixed po doses, steady-state levels are achieved in 7—10 days. Phenytoin is metabolized in the fiver to inactive metabolites. The plasma half-life is approximately 22 h. Phenytoin is excreted primarily in the urine as inactive metabolites and <5% as unchanged dmg. It is also eliminated in the feces and in breast milk (1,2). Prolonged po use of phenytoin may result in hirsutism, gingival hyperplasia, and hypersensitivity reactions evidenced by skin rashes, blood dyscrasias, etc... 

Phenytoin, trimethadione, valproic acid Antithyroid drugs Methimazole Chelators... 

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).

B. Johansson, Simplified quantitative determination of plasma phenytoin on-line pre-column high-perfor mance liquid immunoaffinity cliromatogr aphy with sample pre-purification , J. Chromatogr. 381 107-113 (1986). 

Quingestanol acetate Stanzolol Tegafur Tiopronin Tocainide Vindesine Xipamid 2oxazo lamina Ammonium acetate Cyclopentamine HCl Ammonium carbonate Aminosalicylic acid Phenytoin... 

Mepenzolate bromide Pipenzolate bromide Pipoxolan HCI Benzoic anhydride Flavoxate HCI Benzonitrile Fentiazac Benzophenone Diphenidol Phenytoin 1,4-Benzoaquinone Dobesilate calcium Ethamsylate Megestrol acetate Benzotetronic acid... 

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