A correlation between renal morphology and renal circulation in pediatric nephrotic syndrome.

A morphometric analysis of the renal biopsy specimens and intrarenal hemodynamic study were performed in 37 pediatric patients with idiopathic nephrotic syndrome. The study indicated an inverse correlation between intrarenal hemodynamics (renal plasma flow and peritubular capillary flow) and a relative area of renal cortical interstitium. In respect to the glomerular study, the incidence of glomerulosclerosis increased as the renal perfusion decreased, however, the correlation did not reach a statistical significance.

Use of drugs and adverse reactions in medical inpatients.

An one-day survey of 111 medical inpatients admitted to four wards of the Department of Medicine, Chulalongkorn University Hospital was conducted. Its aim was to examine the differences in medication use patterns and incidence of adverse reaction to medication between young and old patients. The mean age and its standard deviation were 43.5 and 18.2 years respectively. Common medications used by these patients were antibiotics, paracetamol, parenteral fluid, peptic ulcer and gastritis remedies, vitamin and mineral supplements, and diuretics. Compared to the young patients, the elderly patients received more prescriptions for cardiovascular drugs and diuretics while receiving fewer prescriptions for vitamin and mineral supplements. Thai elderly medical inpatients had a higher rate of adverse reaction when compared to their young counterparts. Patients who received 6 medications or more were more likely to have an adverse reaction than those who received less than 6 items. The discipline of geriatric medicine may have a role in caring for the elderly patients in medical wards. A cohort study with a larger sample for determining causes or factors associated with adverse drug reactions is needed.

The effect of aging on the pharmacokinetics and pharmacodynamics of prazosin.

OBJECTIVE: The effect of age on the pharmacokinetics and pharmacodynamics of prazosin (alpha 1 adrenoceptor blocker) was studied in 20 healthy volunteers. PATIENTS: Ten elderly (61-81 y) and ten young (23-28 y) subjects were studied. All subjects received 1 mg of prazosin orally in a fasting state. Serial blood samples were collected for calculation of oral pharmacokinetics, and blood pressure and pulse rate were measured during blood collection. Subjects remained supine and fasting for the first three hours post drug administration, after which they were allowed to ambulate and eat. RESULTS: The oral pharmacokinetics of prazosin were not different in the two age groups. The serum t1/2 in the elderly was 210 min while in the young group was 139 min. The AUC(zero)-infinity in the two groups was not different. The Cmax was identical in the two groups, and the time to Cmax was 84 min in the elderly and 114 min in the young subjects. Protein binding was 93.4% in the elderly and 93.5% in the young subjects and the serum alpha 1 acid glycoprotein concentration was not different in the two groups of subjects. Even though the pharmacokinetics of prazosin were unchanged by age, the haemodynamic effects of the drug were greater in the elderly. The fall in systolic blood pressure and mean blood pressure was significantly greater in the elderly group at multiple time points after drug administration while the change in diastolic blood pressure was equivalent in the two age groups. Despite a greater decrease in mean blood pressure in the elderly, the compensatory increase in heart rate was similar in the two age groups suggesting a difference in the baroreceptor reflex in the two age groups. CONCLUSION: The results of this study demonstrate that age does not alter the pharmacokinetics of oral prazosin, but the pharmacodynamic response at equivalent plasma prazosin concentration is greater in the elderly.

The role of adenosine in promoting cardiac beta-adrenergic subsensitivity in aging humans.

The mechanism by which aging decreases the cardiac chronotropic response in human subjects is unknown. We investigated the role of endogenous adenosine in attenuating the chronotropic response to beta-adrenoceptor stimulation due to aging by employing the adenosine receptor antagonist, theophylline. Sixteen healthy elderly (67.1 +/- 1.3 yrs) and sixteen healthy young (26.1 +/- 0.6 yrs) subjects were studied. The bolus dose of isoproterenol necessary to increase the heart rate 25 beats per minute (I25) was determined by calculating the log dose response curve before and after a 30-min infusion of theophylline (6.5 mg/kg) in each subject. In addition, the effect of theophylline on the orthostatic increase in plasma renin activity (PRA) was determined. The I25 for the elderly and young groups were 34.55 +/- 6.98 and 10.85 +/- 1.93 ng/kg, respectively (p < .01). After theophylline administration, the difference in I25 in the two groups was no longer present (13.32 +/- 2.72 vs 7.46 +/- 1.26 ng/kg). The dose ratios (I25 after theophylline/I25 before theophylline) in the elderly and young groups were 0.43 +/- 0.06 and 0.82 +/- 0.14, respectively (p < .05). After the administration of theophylline, the orthostatic increase in PRA was enhanced more in the elderly subjects (0.53 +/- 0.23 vs 1.54 +/- 0.35 ng AI/ml/hr; p < .01) than in the young (1.31 +/- 0.23 vs 2.49 +/- 0.53 ng AI/ml/hr; p-value n.s.). Plasma norepinephrine changes after theophylline and postural norepinephrine changes after theophylline were not different in the two age groups. Excessive adenosine production or effect is partly responsible for the cardiac chronotropic resistance to isoproterenol and the diminished postural change in PRA in the elderly.