Gentamicin and renal failure

Impaired Renal Function Secondary to Gentamicin — Identifying the Special Risk Patient

Although gentamicin has been commercially available since 1969, reports concerning the incidence of nephrotoxicity from this drug and variables relating to this toxicity are still unclear and conflicting. In view of this, a prospective study of patients receiving gentamicin over a two month period was undertaken to determine the incidence of nephrotoxicity and to study the influence of several variables on the potential for developing gentamicin associated nephrotoxicity. The variables studied were patient's age; the total grams of gentamicin received; the total number of days the patient received gentamicin with a hemoglobin of less than 12 g%; sex; total days duration of therapy; hemoglobin prior to therapy; hematocrit prior to therapy; red blood cell count prior to therapy; albumin level prior to therapy; and if the patient received another potentially nephrotoxic drug concomitantly with gentamicin. Sixty patients in total were studied. However, in the “toxic” and “nontoxic” grouping process, seventeen patients were excluded from the study due to missing variables. Of the remaining sample, ten patients were classified as “toxic” and thirty-three were classified as “nontoxic.” Thus the incidence of nephrotoxicity was at least 10/60 or 16.7 percent. The data relating to the variables identified were analysed utilizing Chi-square, t-test, and multiple regression analyses. Two variables were found to be highly significant in relationship to the development of nephrotoxicity while receiving gentamicin therapy. These were (1) the albumin level prior to therapy (lower albumin level in the “toxic” group) and (2) the concomitant use of another potentially nephrotoxic drug. The mechanism behind the influence of albumin on gentamicin toxicity is unclear, but may be related to protein binding. The basis for nephrotoxicity relating to combined use of nephrotoxic drugs is probably additive or synergistic toxicity but this is also unclear.

Until larger prospective studies concerning gentamicin associated nephrotoxicity provide more meaningful information concerning the significance of the variables involved in this adverse reaction, caution is recommended when using this drug in the albumin deficient patient or in combination with nephrotoxic drugs. In addition, it is further recommended that in patients receiving gentamicin, renal function should be closely monitored and the dosage regimen determined accordingly.

CCL2/CCR2 chemokine signaling coordinates survival and motility of breast cancer cells through Smad3 protein- and p42/44 mitogen-activated protein kinase (MAPK)-dependent mechanisms

Increased cell motility and survival are important hallmarks of metastatic tumor cells. However, the mechanisms that regulate the interplay between these cellular processes remain poorly understood. In these studies, we demonstrate that CCL2, a chemokine well known for regulating immune cell migration, plays an important role in signaling to breast cancer cells. We report that in a panel of mouse and human breast cancer cell lines CCL2 enhanced cell migration and survival associated with increased phosphorylation of Smad3 and p42/44MAPK proteins. The G protein-coupled receptor CCR2 was found to be elevated in breast cancers, correlating with CCL2 expression. RNA interference of CCR2 expression in breast cancer cells significantly inhibited CCL2-induced migration, survival, and phosphorylation of Smad3 and p42/44MAPK proteins. Disruption of Smad3 expression in mammary carcinoma cells blocked CCL2-induced cell survival and migration and partially reduced p42/44MAPK phosphorylation. Ablation of MAPK phosphorylation in Smad3-deficient cells with the MEK inhibitor U0126 further reduced cell survival but not migration. These data indicate that Smad3 signaling through MEK-p42/44MAPK regulates CCL2-induced cell motility and survival, whereas CCL2 induction of MEK-p42/44MAPK signaling independent of Smad3 functions as an alternative mechanism for cell survival. Furthermore, we show that CCL2-induced Smad3 signaling through MEK-p42/44MAPK regulates expression and activity of Rho GTPase to mediate CCL2-induced breast cancer cell motility and survival. With these studies, we characterize an important role for CCL2/CCR2 chemokine signaling in regulating the intrinsic relationships between breast cancer cell motility and survival with implications on the metastatic process.

Effect of recombinant human erythropoietin on new anaemic model rats induced by gentamicin

The effects of recombinant human erythropoietin (r-HuEPO) on haematological parameters were studied in rats in which uraemia and anaemia had been induced by gentamicin, an aminoglycoside antibiotic and a nephrotoxic agent. After the occurrence of slight polycythaemia, the red blood cell count, haematocrit and haemoglobin concentration decreased by 20-30% compared with those of the control (saline-injected) rats. At the end of gentamicin treatment, the endogenous serum EPO level had decreased to about 40% compared with that of control rats. Gentamicin-treated rats showed marked elevation of blood urea nitrogen, extensive tubular necrosis in the kidney and haemosiderin deposition in the spleen. In the osmotic fragility test, the fragility of erythrocytes significantly increased compared with that of control rats. These findings indicate that the anaemia induced by gentamicin is due not only to a deficiency of EPO but also to an enhancement of fragility of erythrocytes in an azotaemic environment. The administration of r-HuEPO during anaemia markedly increased red blood cell count, haematocrit and haemoglobin concentration. It is suggested that a gentamicin-treated rat is a useful and convenient anaemic model and r-HuEPO is useful for treatment of anaemia in acute renal failure.

Biochemical effects of gentamicin on rat kidney cortex. II. Analytical subfractionation after short-term, high-dose treatment

As a first step in studies on the molecular mechanism(s) underlying gentamicin toxicity, the effect of treating rats with this aminoglycoside antibiotic (100 mg/kg once or twice daily for 3 days) on the analytical subfractionation of the kidney cortex has been examined. DNA was used as a marker for the nuclei, cytochrome oxidase for mitochondria, acid phosphatase for lysosomes, catalase for peroxisomes (with reservations; see the companion paper), NADPH-cytochrome c reductase for the endoplasmic reticulum, p-nitrophenyl-alpha-mannosidase (at pH 5.5) for the Golgi apparatus, AMPase for the plasma membrane in general and alkaline phosphatase for the brush border, and lactate dehydrogenase for the cytosol. In addition, the presumptive lysosomal hydrolases N-acetyl-beta-D-glucosaminidase, p-nitrophenyl-alpha-mannosidase (at pH 4.5), cathepsin D, and DNase II were monitored. Electron microscopy was also performed on the subfractions obtained. The only significant biochemical changes brought about by gentamicin treatment were that N-acetyl-beta-D-glucosaminidase demonstrated both a greater total activity and a larger enrichment in the 104,000gav pellet, while p-nitrophenyl-alpha-mannosidase at pH 4.5 demonstrated the same total activity and a greater enrichment in the 104,000gav pellet. Since myeloid bodies were shown by electron microscopy to sediment primarily with the 500gav and 10,000gav pellets, the biochemical changes seen cannot be associated with these morphological structures. These findings suggest that selective changes in a certain subpopulation(s) of lysosomes or in certain lysosomal enzymes may be involved in the early stages of gentamicin toxicity. On the other hand, no lysosomal membrane damage was observed here, since both the latency of acid phosphatase and the recovery of this activity in the soluble cytosol were unchanged. The present investigation may also have relevance for the dosage and duration of gentamicin treatment chosen in clinical situations.

Benefit-risk assessment of investigational drugs: current methodology, limitations, and alternative approaches

Development of investigational drugs is a process integrated traditionally into four overlapping phases. The goal is to introduce new therapies to clinical medicine by assessing benefits and risks associated with administering the new drug. Benefit assessment is performed with respect to the disease for which the drug may comprise an effective treatment. In contrast, safety assessment is relatively standardized across many pharmacologic classes of agents. For purposes of benefit-risk assessment, investigational drugs are developed to provide benefit in three major disease categories: acute, episodic, and chronic. Benefit assessment is the major focus of conventional methodologies. Inherent limitations of risk assessment produced by conventional approaches are illustrated by the historical inability to detect toxicities of various drugs until large patient populations have been treated, typically after the drug is marketed. Alternative approaches to overcome these limitations include assessment of safety in studies specifically designed to optimize such evaluation and more extensive safety testing of investigational drugs in patient subgroups at higher risk. Such approaches serve the interest of patients, physicians, and developers by facilitating the development of new therapies by providing a more complete benefit-risk assessment prior to initial marketing of the drug.

Cortical and papillary absorptive defects in gentamicin nephrotoxicity

Renal function was examined in rats given daily injections of gentamicin (100 to 150 mg/kg) for 10 to 14 days. Whole kidney inulin clearance fell and urine volume increased. Single nephron GFR of surface nephrons varied. Some nephrons had no filtration, some had low rates, and some had high rates. Abnormal renal tubular epithelial inulin permeability was demonstrated by microinjection. Micropuncture of individual nephrons early and later in their course demonstrated reduced fluid reabsorption along the proximal convoluted tubule of superficial nephrons. Rates of fluid delivery to the late proximal and distal tubule were elevated. The rate of fluid reabsorption in the superficial loop of Henle was increased. Maximal urine osmolality and papillary tissue content of urea was reduced. The polyuria, therefore, results from decreased fluid reabsorption by proximal tubules and, probably, by papillary collecting ducts. The decrease in proximal fluid reabsorption is probably secondary to impaired solute reabsorption. A decrease in collecting duct fluid absorption can be attributed to the observed decrease in papillary solute concentration.

Pathophysiology of altered glomerular function in aminoglycoside-treated rats

To evaluate the relative influences of gentamicin and tobramycin on glomerular function, we studied three groups of normal hydropenic rats. Group 1 had 8 rats that served as control. Group 2 had 9 rats that were given gentamicin (40 mg/kg of body wt per day for 10 days). Group 3 had 10 rats that received tobramycin instead of gentamicin. In addition, we attempted to suppress angiotensin II (AII) generation in two additional groups of rats and then study the glomerular response to gentamicin: in 6 rats, isotonic sodium chloride was substituted for tap water for drinking throughout the period of study (group 4), and in 7 other gentamicin-treated rats, captopril was given orally (group 5). A sixth group received captopril alone (group 6). Following gentamicin treatment in group 2, values for single nephron GFR (SNGFR) were markedly lower (21.7 +/- 2.1 nl/min) than they were in groups 1(35.7 +/- 1.4) or 3(34.1 +/- 2.9). Declines in whole kidney GFR in group 2 paralleled the fall in SNGFR. Reduction in SNGFR with gentamicin was due both to a marked decline in the glomerular capillary ultrafiltration coefficient, Kf, and in the initial glomerular plasma flow rate, QA. With saline administration (group 4), the decline in SNGFR was partially blunted, whereas with captopril (group 5) the effects of gentamicin on SNGFR, QA, and Kf were largely abolished. Morphologic studies revealed no discernible glomerular defects in any groups, whereas proximal tubule damage was evident with both aminoglycosides, irrespective of the state of the renin-angiotensin system. Thus, in the dosage used, gentamicin elicits greater impairment in glomerular function than does tobramycin, and by mechanism(s) that are at least partially responsive to suppression of AII generation.

Effect of osmotic diuresis on gentamicin-induced nephrotoxicity in rats

The effect of isosorbide diuresis on gentamicin excretion and tissue accumulation as well as gentamicin-induced histopathologic changes in renal tissue were examine in rats. Gentamicin (30, 60, 120, 160 mg/kg) was administered s.c. for 10 consecutive days with or without isosorbide pretreatment. Osmotic diuresis with isosorbide did not significantly reduce the dose-dependent extent of gentamicin accumulation in renal tissues in comparison to nondiuresed rats. Although the urinary concentration of gentamicin was reduced in the diuresed animals, total gentamicin excretion remained unaffected. In addition, diuresis altered neither the renal excretion of the proximal tubular cell marker enzyme, N-acetyl-B-glucosaminidase, nor the severity of pathologic damage as determined by light microscopic examination of renal tissues. It appears that osmotically-induced diuresis alone is insufficient to prevent or significantly reduce gentamicin nephrotoxicity in rats. This is in contrast to other forms of diuretic therapy, such as furosemide, which have been shown to effectively reduce renal accumulation and resultant renal toxicity of aminoglycoside administration.

Course of gentamicin nephrotoxicity

Metabolic balance and morphologic studies were performed on rats receiving gentamicin 100 mg/kg/day for a period of 8--10 days and during the recovery period. Daily urine flow rate increased with the administration of gentamiccin and remained elevated up to 20 days following the discontinuation of gentamicin, although BUN and plasma creatinine were virtually normal 10 days after the discontinuation of gentamicin. During the development of renal failure means daily electrolyte excretion remained normal. During the recovery period, however, sodium and potassium excretion exceeded control values while chloride and net acid excretion remained normal. Proteinuria developed during the administration of gentamicin and returned to normal 6--10 days after the discontinuation of gentamicin. Ten days of netilmicin administration (150 mg/kg/day) resulted in only mild tubular degeneration and no azotemia.

Fanconi syndrome associated with cephalothin and gentamicin therapy

A case is reported of Fanconi syndrome and nonliquric renal failure, following a brief course of cephalothin and gentamicin, in a patient with diffuse histiocytic lymphoma. These drugs, especially when used in combination, have been associated with nephrotoxicity manifested as acute tubular necrosis and altered proximal tubular function, but biochemical evidence for generalized proximal tubular dysfunction has not been accurately defined. Thus far, only two other antibiotics, degraded tetracycline and streptozotocin, have been implicated in producing an acquired Fanconi syndrome.

Mechanisms of the defect in glomerular ultrafiltration associated with gentamicin administration

Micropuncture studies were performed in three groups of Munich-Wistar rats: eight normal hydropenic controls (group I) and two groups (eight rats each) which were treated with gentamicin in doses of either 4 or 40 mg/kg/day for ten days (groups II and III, respectively). Following gentamicin administration, values for single nephron (SN) GFR were reduced markedly, from the control mean of 31 +/- 0.7 (SEM) nl/min to 22.4 +/- 1.5 and 20.5 +/- 0.9 for groups II and III, respectively. Declines in whole kidney GFR paralleled these falls in SNGFR. The primary cause of the reduction in SNGFR was a marked decline in glomerular capillary ultrafiltration coefficient, Kf, in both gentamicin treatment groups. None of the other determinants of glomerular ultrafiltration were significantly affected in the low dose group (group II). In the high dose group (group III), however, mean values for initial glomerular plasma flow rate and mean transglomerular hydraulic pressure difference were significantly lower than in the control group, accounting for the somewhat greater decline in SNGFR observed in group III. Electron microscopic examination of kidney tissue from rats treated with both doses of gentamicin revealed no obvious abnormalities of the glomerular capillary wall, whereas the previously described morphologic aberrations of proximal convoluted tubule cells were readily demonstrable.

Gentamicin-induced nephropathy

162 consecutive gentamicin courses have been evaluated retrospectively with respect to nephrotoxicity of gentamicin (GM). Of these, 120 courses were administered in 106 patients for more than 2 days and under adequate control of plasma creatinine (PCr). In 62 of these 120 courses, PCr concentrations increased. In 17 courses (14%), GM therapy was found to be the only demonstrable etiology to the rise in PCr. The 17 courses with GM-induced reduction in kidney function were characterized by a prolonged duration of treatment, a high total dose of GM and a somewhat higher level of serum GM than the 58 courses of GM treatment in which PCr remained unchanged. No significant differences were found with regard to age, average daily dose of GM, average daily dose per kg and average daily dose in proportion to average diuresis. Additional administration of other nephrotoxic drugs did not increase the incidence of GM-induced nephropathy. When GM was the only demonstrable cause of nephropathy, the elevation in PCr concentrations were generally mild and transient, while the nephropathy when other factors were involved more often became severe and occasionally irreversible.

Nephrotoxicity of cephalosporin-gentamicin combinations in rats

TO STUDY THE POSSIBILITY THAT CEPHALOSPORINS AUGMENT THE NEPHROTOXICITY OF GENTAMICIN, GROUPS OF RATS WERE GIVEN FOUR HOURLY SUBCUTANEOUS DOSES OF: gentamicin (5 mg/kg), gentamicin plus cephalothin (100 mg/kg), gentamicin plus cefazolin (20 mg/kg), gentamicin plus cefazolin (50 mg/kg), gentamicin plus cephaloridine (50 mg/kg), or saline diluent for 15 days. Periodic measurements were made of urine volume, urine osmolality, urine protein excretion and lysosomal enzymuria, as well as blood urea nitrogen, creatinine clearance, and drug concentrations in renal cortex and medulla. Tissue was examined by light and electron microscopy. Enzymuria and proteinuria increased early in the course of all treatment groups, whereas urine osmolality declined. No distinct patterns of these variables were discernable among the groups. Gentamicin alone, gentamicin plus cephalothin, and gentamicin plus cefazolin (20 mg/kg) caused the same significant fall in glomerular filtrate rate from control values by day 15 (P < 0.05). Gentamicin plus cefazolin (50 mg/kg) and gentamicin plus cephaloridine failed to cause a decline in glomerular filtration rate compared with controls (P > 0.05). Gentamicin concentrations in renal cortex were 5 to 10 times higher than those in medulla in all groups. Cephaloridine and cefazolin (50 mg/kg) also displayed a gradient pattern in renal cortex, whereas cephalothin and cefazolin (20 mg/kg) did not. Cytosegrosomes with myeloid figures were characteristic ultra-structural changes seen in all groups; however, they tended to be smaller with less numerous myeloid bodies in the groups receiving gentamicin plus cephalothin, cefazolin (50 mg/kg), or cephaloridine. Cephalosporins did not augment gentamicin toxicity. High doses of cefazolin and cephaloridine protected kidneys from gentamicin nephrotoxicity. The protection may involve intracellular drug interaction within the renal cortex.

Association of renal injury with combined cephalothin-gentamicin therapy among patients severely ill with malignant disease

There is a high incidence of primary renal tubule damage among patients with malignant disease who die following recent treatment with combinations of cephalothin and gentamicin. Administration of this combination of antibiotics appears to make the patient appreciably more susceptible to severe renal injury if an additional, often minor, insult to the renal tubules is superimposed. In the present study, significant blood loss or bacterial infection not promptly controlled by the antibiotic combination were two factors that provided this additional insult to many patients; the renal injury in these patients could not be attributed to bleeding or infection alone. The combination of cephalothin plus gentamicin carries the potential of causing renal tubule injury and places the patient severely ill with malignant disease at risk for renal failure from many clinical complications which are commonly associated with their primary illness.

Renal damage caused by gentamicin: a study of the effects on renal morphology and urinary enzyme excretion

Gentamicin sulphate was administered to male Wistar rats by intramuscular injection at varying dosage and for varying periods. At high dosage (50-100 mg/kg/day) gentamicin causes tubular necrosis. At dosages equivalent to that given to man (5 mg/kg/day) obvious degenerative changes are produced. Similar changes are seen in human tubular epithelium and urine deposits of patients treated with gentamicin. There is increased excretion of urinary enzymes proportional to the degree of tubular damage. The importance of these changes in man is stressed.

Evidence of gentamicin nephrotoxicity in patients with renal allografts

Renal damage was assessed by measuring urinary enzyme excretion in 180 patients with renal allografts. Thirty-six of these patients were studied during 53 courses of treatment with antimicrobial agents which was the only antimicrobial agent which was associated with an increase in urinary enzyme activity. There was usually also evidence of reduced renal function. Renal morphological changes similar to those produced by gentamicin in rats were observed in human allograft biopsy specimens obtained during gentamicin treatment.

Enzymuria in gentamicin-induced kidney damage

To assess their potential value as early indicators of gentamicin-induced kidney damage, lysosomal hydrolases were measured in the 24-h urines of rats receiving 30 or 60 mg of gentamicin per kg per day for 15 days. Proteinuria, urine osmolality, blood urea nitrogen, and creatinine clearance were also measured. Kidney tissue was examined by both light and electron microscopy. Beta-galactosidase, beta-n-acetyl-hexosaminidase, and alpha-fucosidase were sensitive indicators and were significantly elevated above control values by day 3 at both doses (P < 0.01). Proteinuria, urine osmolality, and tests reflecting glomerular filtration rate were later indicators of nephron damage. Changes by light microscopy were detected on day 5. Necrosis was most prominent in the proximal convoluted tubules on day 10. Electron microscopy revealed numerous cytosomes with myeloid bodies within the proximal tubular epithelium on day 5. Lysosomal enzymuria appears to be an early manifestation of gentamicin nephrotoxicity and may possibly be related to the lysosomal abnormalities seen on electron microscopy.