Toxicology
In a few specific poisonings additional biochemical tests may be of value (Table 60.1).
Table 60.1
Toxins for which biochemical tests are potentially useful
| Toxin | Additional biochemical tests |
| Amphetamine and Ecstasy | Creatine kinase, AST |
| Carbon monoxide | Carboxyhaemoglobin |
| Cocaine | Creatine kinase, potassium |
| Digoxin/cardiac glycosides | Potassium |
| Ethylene glycol | Serum osmolality, calcium |
| Fluoride | Calcium and magnesium |
| Insulin | Glucose, c-peptide |
| Iron | Iron, glucose |
| Lead (chronic) | Lead, zinc protoporphyrin |
| Organophosphates | Cholinesterase |
| Dapsone/oxidizing agents | Methaemoglobin |
| Paracetamol | Paracetamol |
| Salicylate | Salicylate |
| Theophylline | Glucose |
| Warfarin | INR (prothrombin time) |
Measurement of drug levels
Usually knowledge of the plasma concentration of a toxin will not alter the treatment of the patient. Toxins for which measurement is useful include carbon monoxide, iron, lithium, paracetamol, paraquat, phenobarbital, phenytoin, quinine, salicylate and theophylline. Quantitative analysis will give an indication of the severity of the poisoning and serial analyses provide a guide to the length of time that will elapse before the effects begin to resolve (Fig 60.1).
