The in vitro effect of drugs on biochemical parameters determined by a SMAC system

1. We have studied the in vitro effect of 39 drugs on 17 biochemical parameters determined by a SMAC System. Only two drugs were found to interfere: ascorbic and theophyline. 2. The ascorbic acid lowers the glucose and the bilirubine values; it increases the creatinine and the uric acid concentration. At concentration smaller than 5 mg/dl of this drug, these effects are negligible. 3. We have found a new drug interference: theophylline inhibits the alkaline phosphatase and LDH activities. This effect is not negligible on alkaline phosphatase for therapeutic levels of this drug; the action on LDH can be ignored at normal therapeutic range. 4. For a given drug, we have found different interference with biochemical parameters determined with various commercial lyophlised control sera or a liquid pool of sera. This indicates that the type of sera used in drug interference studies must be described.