... of cocaine into ben-zoylecgonine but in accumulation of ecgonine methyl ester by the action of the coexisting cholinesterase [ 13] . erefore, the cocaine concentration in blood at the point of ... phenobarbital, phenytoin, ephedrine, diazepam, nordiazepam, lidocaine, methamphetamine, codeine, barbital, zotepine, amitriptyline and nortriptyline.24 Pitfalls and cautions in analysis of drugs ... being recommended. Cocaine seems stable in blood for 2 3 weeks in the presence of NaF in a refrigerator [2]. However, in the case of tetracaine, the addition of neostigmine is necessary in...