Drugs of abuse and renal disease

The complications of drug abuse encompass a spectrum of glomerular, interstitial, and vascular diseases. They comprise the heroin-associated nephropathy seen in African-American intravenous drug addicts, which, however, has given way in the 1990s to HIV-associated nephropathy. Infections with methicillin-resistant Staphylococcus aureus may cause acute glomerulonephritis by releasing bacterial superantigens. Hepatitis C has supplanted hepatitis B and may give rise to membranoproliferative glomerulonephritis and cryoglobulinemia. Addicts who inject drugs subcutaneously ('skin popping') may develop amyloidosis. Cocaine causes rhabdomyolysis, severe hypertension, occasionally renal failure in the absence of rhabdomyolysis, and may hasten progression to uremia in patients with underlying renal insufficiency. 'Ecstasy', an amphetamine-like recreational drug, has caused acute renal failure, electrolyte disturbances, and malignant hypertension. In Belgium and some other European countries, women taking Chinese herbs in a slimming regimen have developed a severe and irreversible interstitial fibrosis that is assuming epidemic proportions.

Factors determining hemoglobin carbamylation in renal failure

Carbamylated hemoglobin (carhb) is formed by the reaction of hemoglobin with cyanate, a product of in vivo urea dissociation. It is found in high levels in patients with renal failure and may be useful in their clinical evaluation. Accordingly, we measured carhb by HPLC after acid hydrolysis in 73 patients with renal failure and 11 controls. Mean carhb levels (expressed as micrograms valine hydantoin/g Hb), were highest in chronic renal failure (CRF, 146 +/- 13), intermediate in end-stage renal disease on hemodialysis (ESRD, 106 +/- 7), and lowest in acute renal failure (ARF, 80 +/- 12) when compared to normal subjects (27 +/- 2). In all patients carhb was significantly correlated with BUN but not with creatinine, bicarbonate, or phosphate. For any level of BUN above 80 mg/dl, carhb was substantially higher in CRF than in ARF. Predialysis BUN and urea reduction ratio (URR) were significant predictors of carhb in ESRD. To investigate the effect of time of exposure and BUN level on the rate of carbamylation of hemoglobin, blood from normal subjects and dialysis patients was incubated in vitro with urea equivalent to BUN levels of 50, 100, 150, and 200 mg/dl and assayed for carhb at 0, 5, 9, and 14 days. Carhb increased linearly over the first nine days of urea exposure and leveled off thereafter. The rate of carbamylation increased as BUN increased and was significantly higher in hemoglobin from dialysis patients than from normal subjects. These results show that the higher the level of carhb at baseline, the higher the rate of carbamylation upon exposure to increasing urea concentrations. We conclude that carhb formation is dependent on urea concentration and length of exposure to urea. The rate of carhb formation for a given urea concentration is greater in hemoglobin already carbamylated, and this may explain why carhb is higher in CRF than in ARF at BUN levels greater than 80 mg/dl. Carhb may thus be a useful index of the duration and degree of exposure to high blood urea levels in patients with renal failure, and may potentially serve as an index of the adequacy of dialysis.

Once weekly intravenous calcitriol suppresses hyperparathyroidism in hemodialysis patients

Although thrice weekly intravenous calcitriol therapy suppresses parathyroid hormone in end-stage renal disease patients, the efficacy of once weekly administration is not known. Sixty-three patients hemodialyzed for a mean duration of 44 +/- 4 months were treated with once weekly intravenous calcitriol at a mean dose of 2.8 +/- 1 microgram/week. Parathyroid hormone was significantly suppressed from a mean baseline level of 471 +/- 38 to 342 +/- 46 at 5 months and 220 +/- 40 pg/ml at 7 months of therapy. Plasma calcium levels rose from 9.0 +/- 0.1 to 9.4 +/- 0.1 and 9.9 +/- 0.2 mg/dl, respectively. Plasma phosphate level was unchanged. No untoward side effects were observed. The same mean dose of calcitriol achieved a comparable degree of parathyroid hormone suppression regardless of whether patients were on prior thrice weekly or no prior therapy. In patients who had been treated with thrice weekly bolus injections, switching to a once weekly bolus injection achieved a comparable suppression with a 36% reduction in the cumulative dose. Thus, once weekly intravenous bolus administration of calcitriol resulted in a rapid and marked suppression of parathyroid hormone, similar in adequacy to thrice weekly boluses but at a considerably lower cumulative weekly dose. Results were particularly impressive in patients recently starting dialysis, suggesting that once weekly administration is safe, cost effective, and should become standard therapy.

Effect of acute and chronic glutathione depletion on renal function in the rat

Renal function was evaluated in normal and acid-loaded rats following acute and chronic depletion of glutathione (GSH) by buthionine sulfoximine (BSO). Creatinine clearance and fractional excretion of electrolytes were normal. There was no acidification or concentration defect detected in animals with acute or chronic GSH depletion.