Left brain, retrotransposons, and schizophrenia.

An increasing part of the work of chemical pathology laboratories in district general hospitals is measuring drug concentrations in plasma, both for toxicological (overdose) diagnosis and for therapeutic monitoring. It is these laboratories , and not specialised toxicological units or departments of pharmacy or clinical pharmacology, that now carry out most such tests on patients. Are clinicians (including nurses), clinical pharmacologists, pharmacists, and the pharmaceutical industry prepared to support the changeover now that substance concentrations are almost universally used for constituents other than drugs and are familiar for drugs in basic research studies? For example, as the molar mass of phenobarbitone is 232 g a plasma phenobarbitone concentration of 4-6 mg/dl becomes 0-2 mmol/l. New ranges for treatment or toxicity would have to be known, but this caused scarcely any problems for the natural constituents. For toxic substances such as ethanol there would be legal implications from the change of units. One of the arguments given against the change is that drugs are administered in mass units, except for intravenous electrolytes; therefore it would be confusing and illogical to quote resultant plasma concentrations in substance units. In practice no confusion arises-for example, in the oral glucose tolerance test, when we investigate whether a dose of 75 g of glucose will raise the two hour blood concentration above 7-0 mmol/l-though, ofcourse, we should say "a dose of 400 mmol." The logical final reform-perhaps hard to accept for clinicians-is that drug dosages should also be stated in substance units; this would require a considerable upheaval in most doctors' and nurses' thinking. Yet a dose as prescribed, in milligrams ofactive drug X, is a round number that often bears little relation to the total mass oftablet which may contain several other pharmaceutical ingredients. The-mass of X itself need not be the same as the mass of drug compound X' in the tablet, which may be present as an ester or hydrated salt-but in substance units X and X' would be identical. If we have round numbers to remember, let them be scientifically consistent and relate to the desired concentrations in plasma. Such an evolutionary change will raise many problems, particularly of safety and of manufacturers' costs, but it could be made. A generation ago, when we changed from imperial (grains and minims) to metric units of dosage (milligrams and millilitres) and everyone had to learn new numbers, were there any lethal consequences or …