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SUMMARY The algorithms used in this hospital to assess calcium status are calculated ionised serum calcium and the serum calcium concentration adjusted for albumin. In order to establish their clinical usefulness, they were compared with the ionised calcium concentration measured on the Nova 2 instrument in patients with various calcium and protein abnormalities. Good correlation was found between the measured and calculated values. The predictive values for the calculated results and for total serum calcium concentrations are presented. In this series, the derived values were useful in predicting the serum ionised calcium concentration of the patients studied.

impaired renal function. Our results indicate that a state ofnarcotic intoxication may exist in the absence of measurable amounts of morphine in the plasma. This may be explained by the persistence in the plasma of large quantities of the metabolite morphine-6-glucuronide, which is usually excreted renally.-Morphine-6-glucuronide (unlike morphine-3-glucuronide) is pharmacologically active in animals and, indeed, may be more potent than morphine itself.4 We believe that our findings are the first-recogised evidence of the pharmacological effect of morphine-6glucuronide in man.Previous studies ofpatients with renal failure seem to have shown abnormal elimination of morphine with reversion to normal when renal function returns after transplantation.' Extensive metabolism of morphine in the kidney has been suggested as a cause of this phenomenon. These findings, however, have been based on a radioimmunoassay for morphine which has been found to cross react extensively with morphine-6-glucuronide.5 Because more of this metabolite than morphine itself remains in the plasma after treatment with morphine, morphine concentrations measured with this radioimmunoassay in fact reflect the sum of morphine and morphine-6-glucuronide present, casting doubt on the results obtained with the assay.The persistence of large amounts of morphine-6-glucuronide in the plasma, as described, is important for several reasons. Firstly, prolonged narcosis, long after the last dose of morphine is given, may result in incorrect diagnosis ofcerebral damage in the obtunded patient. Secondly, respiratory depression lasting for many days exposes the patient to the complications ofintubation and mechanical ventilation.Finally, the fact that morphine-6-glucuronide may have been a confounding factor in many previous studies of morphine pharmacokinetics that used radioimmunoassay suggests that these studies should be re-evaluated, with greater emphasis placed on the role of morphine-6-glucuronide in the clinical effects of morphine.We thank Dr C Hinds, Dr Eight patients with cancer associated hypercalcaemia were treated with the combination of aminohydroxypropylidene diphosphonate and salmon calcitonin for six days. Serum calcium concentration fell significantly within 24 hours of starting treatment due to a reduction in bone resorption and renal tubular calcium reabsorption. In the longer term hypercalcaemia was controlled by a further progressive reduction in bone resorption, which persisted for six days after treatment was stopped. Renal tubular calcium reabsorption, however, remained suppressed

SUMMARY The results of analysis of blood specimens from randomly selected adults aged Adult subjects were selected randomly by computer, as described elsewhere,5 and invited to attend a local health centre. Due to press publicity, a large number of people volunteered to be included. All socioeconomic groups were represented. The age range of the subjects was 19-88 years. BLOOD SPECIMENSThese were taken from the subjects, who were not asked to fast, between 1815 and 2100. Blood was taken from the antecubital vein with the subjects seated. A tourniquet was used only when necessary to locate the vein and released before withdrawal of blood. The blood was collected into tubes containing lithium heparin, and specimens were centrifuged and separated at the end of each session. The separated plasma was stored overnight for analysis the next day. The survey lasted for 13 months.