MRI assessment of drug-induced fluid accumulation in humans: validation of the technology.

PURPOSE: The purpose of this study was to evaluate the feasibility of using proton and sodium magnetic resonance imaging (MRI) to detect fluid accumulation produced by fludrocortisone and nifedipine - two drugs known to cause salt/water retention by different mechanisms. MATERIALS AND METHODS: Twelve young healthy male subjects were randomly assigned to one of two groups and treated with either fludrocortisone or nifedipine for 14 or 25 days, respectively. The change in sodium MRI, as well as in proton T(2) value and T(1)-weighted signal intensity in the calf following postural change [referred to here as 'postural delta signal'(PDS)], was evaluated before, during and after drug administration. The changes in MRI PDS were compared to conventional physiological parameters, including body weight, calf volume and pitting edema. RESULTS: When compared to the baseline pretreatment values, the subjects treated with fludrocortisone showed a 5.5% increase in sodium MRI PDS (P=.01), a 2-ms increase in proton T(2) PDS of the gastrocnemius muscle (P=.06) and a body weight gain of 2.3% (P=.001) within 1 week. In the nifedipine-treated subjects, the sodium MRI PDS increased by 6% versus baseline (P=.03), while the proton T(2) PDS of the gastrocnemius muscle increased by 3.7 ms (P=.01), associated with a 0.5% weight gain (P=.55), within 3 weeks. No significant changes were noted in the T(1)-weighed images following postural change. Measurements of calf circumference, volume and pitting edema did not show consistent changes associated with the drug administration. CONCLUSION: The postural change in sodium MRI and proton T(2) signals provides a sensitive method for detecting the fluid accumulation produced by fludrocortisone and nifedipine. The MRI results are consistent with treatment-induced increases in extracellular fluid volume and correlate well with the observed weight gain. These findings support the potential utility of MRI for the evaluation of medication-induced fluid retention.

[Effect of 9-alpha-fluorhydrocortisone (Florinef) in extrarenal regulation of potassium]. / Efeito da 9-alfa-fluoridrocortisona (Florinef) na regulação extra-renal do potássio.

There are evidences that adrenal hormones regulate extrarenal potassium homeostasis. The present study evaluated the effect of Florinef modulation on extrarenal mechanisms in potassium adaptation of adrenalectomized rats. The results demonstrated that the rats treated with Florinef had serum potassium levels at normal range probably due to an increase in cellular potassium uptake consequently to en enhanced activity of Na-K-ATPase.

Assessment of urine-concentrating ability in man: effect of fludrocortisone and urea in enhancing response to vasopressin.

1. Healthy subjects, given a long-acting preparation of vasopressin intramuscularly, excreted a significantly less concentrated urine than when subjected to fluid deprivation for 28 h. 2. When fludrocortisone, a potent mineralocorticoid, was given in addition to vasopressin the urine was not significantly less concentrated than after fluid deprivation. 3. Oral urea-loading also enhanced the urine-concentrating power of vasopressin but its effect was less marked than that of fludrocortisone. Oral urea did not increase further the urine concentration achieved by combined fludrocortisone and vasopressin. 4. Renal concentrating power was assessed in fourteen patients with renal disease and impaired concentrating ability. Fludrocortisone significantly enhanced the urine concentration achieved by vasopressin alone and the resultant urine was not significantly less concentrated than that achieved by fluid deprivation. 5. The action of fludrocortisone in enhancing the urine-concentrating effect of vasopressin is similar to that of aldosterone and is probably due to the increased sequestration of solute in the renal medulla, caused by increased reabsorption of sodium chloride in the ascending limb of the loop of Henle. 6. In the clinical assessment of renal concentrating power, the combined use of fludrocortisone and vasopressin has potential advantages over established methods.