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The respiratory depression effect of aminoglycoside antibiotics was studied by a toxicokinetic approach, and species differences in drug susceptibility were elucidated based on plasma concentrations. An allometric relationship was obtained between total body clearance of arbekacin, a novel aminoglycoside antibiotic, and animal body weight. The power was 0.714, less than unity, which means smaller animals have higher ability to eliminate the drug from the body and need higher doses to attain a certain steady-state plasma concentration. When the infusion rate of arbekacin was altered, the total dose required to cause the toxicologic endpoint for respiratory depression (60 per cent loss of respiratory rates) changed greatly, but the plasma concentration of arbekacin at the toxicologic endpoint remained at almost a constant level. The concentration at the toxicologic endpoint was similar for all of the animal species examined and was 650-950 micrograms ml-1, even though the total dose required to cause the toxicologic endpoint varied greatly among the animal species. These findings suggest that the toxicologic effect compartment for respiratory depression is indistinguishable from the plasma compartment, and that species differences in the total dose are due to differences in pharmacokinetics of the drug, mainly in the total body clearance, but not to differences in intrinsic susceptibility to the drug.

A 72-year-old woman complaining of somnolence and thirst was diagnosed to have a hypercalcemic crisis (corrected serum calcium level, 17.4 mg/dl) associated with encephalopathy and nephropathy. Imaging diagnostic techniques demonstrated a retroperitoneal tumor at the median site of right renal pelvis. Hormonal studies revealed that plasma levels of thromboxane B2, prostaglandin (PG) E2, 6-keto prostaglandin F1 alpha (PGF1 alpha) and prostaglandin F2 alpha (PGF2 alpha) were markedly elevated. The tumor was successfully removed by operation; her serum calcium level and PG levels normalized without any treatment indicating that this case belongs to the category of humoral hypercalcemia of malignancy (HHM). Pathologically, this tumor was diagnosed to be a benign neurilemoma. Parathyroid hormone-related protein (PTHrP) radioimmunoassay and Northern blot hybridization for PTHrP mRNA were negative. The current case demonstrates that hypercalcemic crisis could be induced by a curable benign neurilemoma, and suggests that this HHM-like morbidity was associated with markedly elevated plasma PG levels.

The complication of Sweet's syndrome and interstitial pneumonia occurred in a patient with myelodysplastic syndrome. Superoxide anion production by the patient's neutrophils was considerably higher than that by neutrophils obtained from normal controls after stimulation with opsonized zymosan, phorbol myristate acetate, or myristic acid. Prednisone, which a potent inhibitor of superoxide anion production by neutrophils, dramatically improved the skin and pulmonary lesions, suggesting that they were parts of the same clinical spectrum associated with the superoxide anion hyperproduction.