Abstract
A gas-liquid chromatographic method for the simultaneous determination of phenobarbital (PB), carbamazepin (Carb), primidone (Prim) and diphenylhydantoin (DPH) in human biological fluids following therapeutic doses has been described.
After extraction with chloroform, the anticonvulsant drugs were methylated with phenyl-trimethylammonium hydroxide in dimethylformamide at 85° for 10 min. Liner temperature programming of a 1% OV-17 column was used to achieve separation and quatitation. The procedure described in the present paper is relatively simple, highly specific and sufficiently sensitive for use in routine clinical assays.
The anticonvulsant drug levels were measured not only in plasma but in saliva. Furthermore, the unbinding drugs in plasma were measured by means of ultrafiltration techniques. Ultrafiltration with using plasma aliquots (1 ml) was performed by an Amincon Centriflo membran cone (CF50) at 20°, 1,000 g for 25 min. It is applicable to screening large samples of patients.
Although it was found a patient having plasma level of 25 μg/ml, which has been considered to be the upper limit of the therapeutic range for DPH, the unbinding fraction in plasma was only 0.7 μg/ml. Thus, it should be noted that a knowledge of unbinding drugs would be more desirable for a therapeutic level than the total drugs level in plasma.
