Risk factors for amphotericin B-associated nephrotoxicity

1 I Risk Factors for Amphotericin MELANIE A. FISHER, M.D., GEORGE MCKEON,

Pharm.D.,

H. TALEIOT, KEVIN P. TYNAN, Pharm.D.,

B-Associated Nephrotoxicity

M.D., GREG MAISLIN, BRIAN L. STROM,

PU~WXE: A case-control study was performed to identify and quantify risk factors for amphotericin B-associated nephrotoxicity. PATIENTS AND METHODS: Thirty-five patients receiving intravenous amphotericin B for treatment of proven or suspected fungal infection who developed nephrotoxicity (greater than 100% increase in baseline serum creatinine to a level above the normal range) were compared with 60 control patients receiving amphotericin B who did not develop nephrotoxicity, Amphotericin B dosing variables and other potential risk factors were analyzed in a logistic regression model. RESULTSCasesof nephrotoxicity received a significantly higher average daily dose of amphoteritin B (0.49 f 0.18 mg/kg/day) than did controls (0.34 f 0.17 n&kg/day). In a multivariate model, the risk of nephrotoxicity increased 3.7-fold for each 50-mg increase in total dose for a fixed duration of therapy and patient weight. Risk decreased by a factor of 0.4 for each extra day of therapy for a fixed total dose and weight. An increase in weight was also protective when the two other dosage variables were held constant. Each 0.10 mg/kg/ day dose increment was associated with a 1.8-fold (95% confidence interval, 1.2 to 2.7) increase in the risk of nephrotoxicity. Other significant risk factors included diuretic use during amphotericin B therapy (12.5,1.7 to 94.7), for which a linear doseresponse relationship was demonstrated, and an abnormal baseline serum creatinine level (15.4, 1.4 to 173.2). CONCLUSION: Risk factors for amphotericin B-associated nephrotoxicity include higher average daily doses(approximately a doubling for each 0.10 n&kg/day increment), diuretic use, and abnormal baseline renal function. These data suggest possible protective interventions and will aid clinicians in assessingthe risk-benefit ratio of amphotericin B therapy for deep fungal infection.

From the Infectious Diseases Section and the Clinical Epidemiology Unit of the Section of General Internal Medicine, Deoariment of Medicine. University of Pennsylvania School of Medicine, and the Department of Pharmacy. HOSDital of the Universitv of Pennsvlvania. Philadelohia. Pennsvlvania. This study was supported in-part by f;nds from the Squibb Corporation. the Rockefeller Foundation, and the Andrew W. Mellon Foundation. Requests for reprints should be addressed to George H. Talbot. M.D., One Gibson Building. Hospital of the University of Pennsylvania,

3400 Spruce Street,

Philadelphia, Pennsylvania 19104. Manuscript submitted 1989. and accepted in revised form July 12, 1989.

January

25.

M.s.,

M.A.,

BERNADE~E

M.D., M.P.H. Philadelphia,

P. Pennsylvania

A

mphotericin B remains the primary drug for the treatment of life-threatening fungal infections. The use of amphotericin B, however, is often limited by its side effects, particularly nephrotoxicity [l]. Soon after the initiation of therapy, the glomerular filtration rate (GFR) decreases nearly 40% in most patients [2]. The GFR often stabilizes at 20%to 60% of normal throughout the course of therapy, but the nephrotoxicity can make management difficult in some patients. Animal and human studies have shown that amphotericin B causes renal insufficiency in at least two ways. First, intense intrarenal arteriolar constriction occurs shortly after the initiation of intravenous amphotericin B therap [3]. Renal plasma flow and GFR then decrease [3-5 r but may be reversed by saline loading [6,7]. Second, after more prolonged treatment afferent arteriolar smooth muscle cells become damaged, causing renal insufficiency [8]. In addition, calcium deposition in the tubules and renal tubular acidosis occur and may contribute to the impairment in renal function [1,9,10]. Although renal insufficiency is a long-recognized complication of amphotericin B therapy, risk factors for amphotericin B-associated nephrotoxicity have never been investigated in a controlled study. Without such data, clinicians have been poorly equipped to determine which patients may experience this complication and what interventions may alter the likelihood of its occurrence. The purpose of this study was to identify and quantify risk factors that predispose a patient to amphotericin B-associated nephrotoxicity.

PATIENTS AND METHODS Hypotheses We postulated that the risk of nepbrotoxicity would be increased by stimuli that reduce renal plasma flow (e.g., sodium depletion, which may occur with diuretics and hypotensive episodes).We postulated further a protective effect of factors leading to an increase in renal plasma flow (e.g., concurrent usage of the sodium-containing antipseudomonal penicilliis such as carbenicillin, ticarcillin, and piperacillin) [6,7]. In addition, we postulated that factors which themselves may induce renal insufficiency might increase a patient’s risk of nephrotoxicity. These factors include the useof intravenous dye, as in radiolo ‘c procedures; diabetes mellitus; aminoglycosides [127; and corticosteroids [13]. We also postulated that liver disease might confer an increased risk becauseof a reported association between cirrhosis and aminoglycoside nephrotoxicity [14]. Finally, we postulated that higher daily and total dosesof amphotericin B would increase the likelihood of renal insufficiency. Patient Population We performed a case-control study that included all adult patients hospitalized at the Hospital of the University of Pennsylvania from January 1981 through December 1983 who received intravenous amphoteritin B for at least two days. Study candidates were

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identified using computerized lists generated in the inpatient pharmacy. Data were collected by patient chart review and recorded on a standardized form by one of the investigators (M.A.F.). Definitions “Baseline serum creatinine” was defined as the lowest average of three consecutive serum creatinine values during amphotericin B therapy or within 72 hours prior to its initiation. “Nephrotoxicity” was defined as a greater than 100% increase in serum creatinine from the baseline value to a level above the normal range during amphotericin B treatment. Nephrotoxicity was considered to have occurred as soon as this threshold was met or exceeded. “Cases” were defined as those patients receiving amphotericin B who developed nephrotoxicity, as defined earlier. “Controls” were those patients receiving amphotericin B who had less than a 50% increase in the serum creatinine level during therapy. An intermediate group of patients had a greater than 50% but less than 100% increase in their serum creatinine level during therapy. This group was excluded from further analysis since it was small in size and we wished to study clinically significant renal insufficiency. Matching Controls were matched to cases by the number of days of amphotericin B exposure to ensure equal periods of observation. When there was more than one control suitable for a case, controls were randomly chosen from among those available. Each control was utilized only once. Most cases had two matched controls. When a case patient had more than one admission for amphotericin B therapy during the study period, he/she was matched to a control also having more than one amphotericin B admission, and the analysis was performed on the corresponding admission.

greater than 40 U/L, or “ascites” listed as a current diagnosis in the chart; fungal disease present or the medical indications for amphotericin therapy (determined from progress notes); toxic aminoglycoside serum levels (defined as a peak of greater than 10 mg/dL for gentamicin and tobramycin and/or trough greater than 2 mg/dL, and for amikacin, a peak of greater than 30 mg/dL and/or trough level greater than 10 mg/dL); and amphotericin B or aminoglycoside therapy during the previous year. Additional variables examined include oliguria (less than 500 mL urine/day); hypotensive episodes (two or more recordings in any one day of a blood pressure less than 80 mm Hg systolic); and exposure to aminoglycosides, corticosteroids, antipseudomonal penicillins, nonsteroidal anti-inflammatory drugs, intravenous contrast dye for radiographs, and other potentially nephrotoxic drugs including intravenous vancomycin, methicillin, methotrexate, and pentamidine. Diuretic exposure was also examined. Patients were categorized into five dosage ranges of furosemide since virtually all first diuretic use was with this agent. The four patients who were given hydrochlorothiazide initially during the study period were converted to an approximate furosemide equivalent by dividing by five. Several patients received a second type of diuretic, mostly metolazone or spironolactone. These patients were considered to have received the largest total dose. The presence of hypercalcemia (serum calcium level greater than 2.7 mmol/L on two or more determinations), hyperuricemia (serum uric acid level greater than 10 mg/dL on two or more determinations), and ureteral obstruction (demonstrated by renal ultrasound and/or intravenous pyelogram) were also examined. Data retrieved from a random sample of 5% of charts were reabstracted by the primary investigator to ensure reliability.

Variables Examined The following variables were examined as potential risk factors: age; race; sex; average daily and total dose of amphotericin B; duration of amphotericin B therapy; underlying renal disease; presence of diabetes mellitus; primary diagnosis (as listed by medical records or in the admission history and physical); liver disease (defined by one of the following diagnoses listed on the face sheet or admission history and physical: “cirrhosis, ” “liver failure, ” “hemachromatosis,” or “hepatitis” or by the presence of at least three of the following abnormalities within seven days of amphotericin therapy: serum albumin less than 30.0 g/L; total bilirubin greater than 43 pmol/L; aspartate aminotransferase greater than 30 U/L; serum alanine aminotransferase

Statistical Analysis Student’s t-test and the Wilcoxon Rank Sum test were used to test for differences between the two study groups. A p value <0.05 was considered significant. For each potential risk factor, a crude odds ratio and 95% confidence interval were calculated. Exact confidence intervals were calculated using Mowan [l5] when any cells in the two-by-two tables had expected values of less than five under the null hypothesis. To control for potential confounding (when sample size permitted), adjusted odds ratios were calculated using multiple logistic regression. The adequacy of the linear model on the logistic scale was assessed by testing the significance of quadratic trend terms added to the model. Although data were collected for several time periods for most of the potential risk factors, only one time period per risk factor was included in the logistic regression model to avoid problems of multicollinearity. The decision not to include the three days prior to the onset of nephrotoxicity for diuretics was done to avoid confusing cause and effect (i.e., diuretics administered to treat oliguria resulting from nephrotoxicity). Similar decisions were made for certain other variables. Possible interactions among the risk factors were evaluated using a screen based on approximate F-tests derived from an estimate of the asymptotic covariance matrix of the beta coefficients [16]. Interaction terms had to meet a minimum sample size requirement to be included in the model; specifically, both of the two-by-two contingency tables (composing

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Data Collection Analysis was performed comparing each patient’s first course of amphotericin B therapy during the hospitalization. The “first course” was defined as the time period during which he/she received amphotericin B at least every other day with no break in therapy of greater than seven days. Exposure to each of the variables of interest was ascertained during three time periods: (1) the three days prior to the onset of nephrotoxicity for the cases; (2) the earlier period of amphotericin B therapy, up until the three days prior to the onset of nephrotoxicity; and (3) the remaining days of hospitalization before amphotericin B therapy began.

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TABLE I

12I IIO 9-

Characteristics

of Study Patients Cases (n = 35)

876-

M&W

5 432I-

7 (20%)

36-49 50-59 m-69 170 I.0

1.5

2.0 Maximum

2.5

3.0

3.5

4.0

4.5

Increase in Creatinine

Figure 1. Maximum increases in creatinine. The maximum increase the serum creatinine from the baseline level is shown as a function the number of patients affected.

I in of

the stratified analysis of the risk factors) had to have all expected cell values greater than five.

RESULTS Thirty-five of the 113 evaluable patients were identified as cases, an incidence of nephrotoxicity of 31%. The mean f SD increment in creatinine from baseline to the onset of nephrotoxicity was 1.3 f 0.5 mg/dL, with a range of 0.6 to 3.2 mg/dL. The mean increment to the peak creatinine level was 1.9 f 1.0 mg/dL (range, 0.6 to 4.8 mg/dL). Figure 1 shows the distribution of maximum increases in serum creatinine. Sixty patients were identified as controls. The remaining 18 patients, who had creatinine increases from 50% to 100% above baseline, were not further analyzed. Demographic and other characteristics of the study population are shown in Table I. The mean average daily dose of amphotericin B for the cases was 0.49 f 0.18 mglkglday, compared with 0.34 f 0.17 mg/kg/day for controls (Table II). Neither total dose nor weight was statistically significantly related to renal failure when the effects were estimated in isolation (Tables II and III). The number of days of amphotericin B therapy was fixed by matching. The mean treatment duration was about 11 days, with a median of seven days. Five cases (14.3%) developed nephrotoxicity after treatment courses of two to three days. A logistic regression model was constructed including the patient characteristic variables listed in Table I (excluding survival), the amphotericin B dose components (Table II), and other potential risk factors (Table III). The following variables were significant: amphotericin B dosing (total dose, weight, and days of treatment); baseline serum creatinine; and diuretic administration between the initiation of amphotericin B and three days prior to nephrotoxicity. In a separate model, we replaced the amphotericin B dosing variables with the single variable, average daily dose in mglkglday. For each 0.10 mg/kg/day increment in dose, the risk of nephrotoxicity increased by a factor of 1.8 (95% confidence interval, 1.2 to 2.7). The data did not confirm an increased risk from exposure to vancomycin, corticosteroids, or radiologic contrast dye. Likewise, no risk was conferred by gender, race, age, admission service, a daily dosing regimen, or by the presence of liver disease, hematologic dyscrasia/malignancy, or underlying fungal disease, although confidence intervals for some of these vari-

16 (27%) lO(lJ%)

7 g;; 5 (144) 8 (23%)

;; {;g{ 9 (lwi)

51.3(17.6)*

50.2 (17.8)

White race

28 (80%)

43 (72%)

Male gender

21(60%)

37 (62%)

Survived

17 (49%)

41(68%)

Admission service Medicine Oncology Other

;; {$jj 8 (23;)

;; $g; 0

18(51%)

31 (52%)

; {;;; 11(3&)

4(7%) 9(15%) 16 (26%)

1; y$,’

33” yg’

Mean age (years)

5.0

Controls (n = 60)

Principal diagnosis Hematologic dyscrasia/ malignancy Cardiovascular Gastrointestinal Other Fungal infection Candidiasis Cryptococcosis Aspergillosis/mucormycosis Other

; y;{

11(18%)

5 (8;) 14 (23%)

0

SD.

TABLE II Average Daily Dose of Amphotericin nents Variable Average daily dose of amphotericin B Ca(sl;lg/k/W9* Control Total dose of amphotericin B (mg) Case Control Pa;;;;

B and Its CompoMaximum

Mean f SD

Minimum

0.49 f 0.18 0.34f 0.17

0.17 0.06

1.05 0.77

366.5f 371.2 261.6 f 276.9

21 11

1,495 1,141

62.5 f 13.4 63.2 f 12.4

i.i

if

weight (kg)

Control Days receiving amphotericin Bt Case Control

10.6 i 8.7 10.8 f 8.7

One control ,.a* subject. was . excluded trom .*.a comparisons average aauy aose sue 10 a mlsslng welgnr value. t Cases and controls were matched on this variable.

2 1 lnvolvlng

ii Weight

an

ables are wide. Data on certain other potential risk factors (e.g., exposure to nonsteroidal anti-inflammatory agents) were insufficient for inclusion in the multifactor model. Exposure to antipseudomonal penicillins was not shown to be protective; in fact, the point estimate suggested the opposite effect. Since similar proportions of casesand controls were exposed to each antipseudomonal penicillin (carbenicillin, ticarcillin, piperacillin, and mezlocillin), a dose-responseanalysis

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AMPHOTERICIN B-ASSOCIATED NEPHROTOXICITY / FISHERET AL rABLE III Risk Factors for Amphotericin

B-Associated Nephrotoxicity Cases*

Variable Total amphotericin 8 dose* Patient weights Amphotericin B (days)** Male gender White race Age (years) Admission service Daily dose regimen Hematologic dyscrasia/ malignancy Candidiasis Baseline creatinine abnormal Diuretics between first amphotericin Band 3 days prior to nephrotoxicity Diuretics within 3 days of nephrotoxicity Diuretics between admission and first amphotericin B Liver disease Aminoglycosides between first amphotericin B and nephrotoxicity Toxic aminoglycoside level prior to nephrotoxicity Toxic aminoglycoside level between admission and first amphotericin B Oliguria prior to nephrotoxicitytt Antipseudomonal penicillin between first amphotericin B and nephrotoxicity Vancomycin between first amphotericin B and nephrotoxicity Steroids between first amphotericin Band nephrotoxicity NSAIDS between first amphotericin B and 3 days prior to nephrotoxicityrr Radiography with contrast dye between first amphotericin Band nephrotoxicity Urinary tract obstruction prior to nephrotoxicityrr Amphotericin B during previous yearrr Diabetes mellitusrr

Crude Odds Ratio (95% confidence interval)

Controls* (See Table II) (See Table II) (See Table II)

;; gq

;; g;;; ’ (See Table I) ’ (See Table I)

;;

yf

0

;;

g;yq

19 (544)

Adjusted Odds Radio (95% confidence interval)+

1.1(0.98-1.1) 0.8 (0.5-1.8) 1.0(0.95-1.1) 1.1(0.5-2.5) 1.6 (0.6-4.3) p = 0.75 p = 0.04 1.1(0.4-2.5) 1.0 (0.4-2.3)

3.7 (1.6-U) 0.2 (0.0549) 0.4 (0.2-0.7) 1.5 (0.3-7.8) 2.4 (0.3-19.4) p = 0.33 p = 0.52 1.9(0.3-11.3) 0.7 (0.1-6.8)

0.4 (0.2X1.8) 2.4 (0.940) 2.6(1.1-6.1)

0.3 (0.04-1.7) 15.4(1.4-173) 12.5 (1.7-94.7)

22 (63%)

17 (28%)

4.3 (1.8-10.4)

-

20 (57%)

27 (45%)

1.6 (0.7-3.8)

-

9 (26%) 22 (63%)

9 (15%) 33 (55%)

2.0 (0.7-5.6) 1.4 (0.6-3.3)

4.3 (0.5-35.6) 0.5 (0.1-3.2)

8 (23%)

5 (8%)

3.3 (1.0-10.5)

0.5 (0.1-5.5)

6 (17%)

4 (7%)

2.9 (0.8-10.7)

-

2 (6%)

1 (2%)

3.6 (0.3-78.6)

-

12 (34%)

15 (25%)

1.6 (0.6-3.9)

2.9 (0.4-24.3)

10 (29%)

8(13%)

2.6 (0.9-7.4)

2.0 (0.2-16.0)

21(60%)

42 (70%)

0.6 (0.3-1.5)

0.2 (0.03-1.5)

4(11%)

2 (3%)

3.7 (0.6-30.2)

7 (20%)

9 (15%)

1.4(0.54.2)

2 (6%)

3 (5%)

1.2 (0.1-7.3)

-

3 (9%)

5 (8%)

1.0 (0.2-4.3)

-

1(3%)

9 (15%)

0.2 (0.01-1.1)

-

2.8 (0.3-25.7)

;AID = nonsteroidal anti-inflammatory drug. lumber and percent with variableidentified. node1 rncludes all varraoles Wlth entrles I” the last column. lfl a separate model. tne total aose. patrent wergnt. ana aays of ampnotericin D variables were replaced tit B”; each 0.10 mg/kg/day increment in average daily dose was associated with a 1%fold (1.2 to 2.7) inby the single variable “average daily dose of amphotericin crt aased risk of nephrotoxicity. B dose: the estimated product increase in the odds of renal failure for every increase of 50 mg in total dose given during the study period. $1 .otal amphotericin odds of renaf failure for every increase of 20 kg in,patient weight. SF‘atient weight: the estimated decreasein,the . l * Uays 01 amphoterlcln U: the eStlmateU decrease I” the odas 01 renal tallrUe lor every One-day Increase In tne study perloo. rf Exact confidence interval used because of the small number of patients with these risk factors present.

adjusting for the differing sodium contents of these was statistically significant for any continuous variantibiotics was not performed. able; therefore, the linear model appeared adequate. To illustrate a dose-responseanalysis for amphotericin B, we plotted the odds ratio for nephrotoxicity asa COMMENTS function of the average daily dosein mg/kg/day (FigAlthough nephrotoxicity is a well-known complicaure 2). tion of amphotericin B therapy, the exact risk factors We further analyzed the effect of diuretic useon the that predisposesomepatients to developing this comrisk of renal failure by examining the total dose-re- plication have not been identified or quantified. The sponserelationship. A statistically significant linear current study has used a retrospective case-control trend (&i-square = 7.4, df = 1, p
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dependent determinants of nephrotoxicity. When the dose components were replaced with a single average daily dose variable in the multifactor model, we found that each 0.10 mg/kg/day increment in dose was associated with a 1%fold increase in the risk of nephrotoxicity. Although the direction of these effects may not surprise clinicians who frequently prescribe amphotericin B, the magnitude of the effects may be unexpected. In addition, quantification of the risks associated with escalating total dose or the average daily dose may assist clinicians in assessing the risk-benefit ratio of high-dose amphotericin B therapy. A primary goal of our study was to identify risk factors that might be amenable to intervention, thereby decreasing the risk of amphotericin B-associated nephrotoxicity. Diuretics administered during the course of amphotericin B until three days prior to nephrotoxicity conferred a 12.5-fold increase in the risk of nephrotoxicity. Diuretics given before the initiation of amphotericin B therapy did not confer an increased risk. Furthermore, a dose-response analysis revealed a statistically significant linear trend (p
&ASSOCIATED

NEPHROTOXICITV

/ FISHER ET AL

.

. . . . 0.0

0.1

0.2

0.3

Average

0.4

0.5

0.6

0.7

0.0

Daily Dose of Ampholeticin (ms / kg /day)

0.9

1.0

1.1

B

Figure 2. Relationship between average daily dose of amphotericin I and the odds ratio for nephrotoxicity. The odds ratio for nephrotoxicity (model derived) is plotted against the average daily dose of amphotericin B in mg/kg/day using the lowest average daily dose level (0.06 mg/kg/day) as the reference. The apparent linearity of the relationship between 0.06 and 0.36 mg/kg/day is due to the scale used to display the odds ratio.

r

None

l-250

Furosemide

251-500

Dose

,500

~1 Compound

(mgs)

L Flgure 3. Relationship between furosemide dose The dose-response relationship between total milligrams and the relative proportion of patients is shown. The term “>l’compound” refers to patients who also received one or more additional

and nephrotoxicity. furosemide dose in with nephrotoxicity furosemide dose in diuretics.

pretation of the data deserves comment in several respects. First, the patient population studied was heterogenous, and included not only patients with hematologic malignancy, but also those with postsurgical fungal infection. Although this may increase the generalizability of our findings, differences among the groups could be missed. Second, although we studied more than 100 patients, the sample size is still relatively small, which may also have obscured someclinically important differences. Third, we did not directly study a “severity of illness” variable, although we did include several proxies for same, including admission service, diagnosis of hematologic dyscrasia or malignancy, and underlying fungal infection. Fourth, our study examined risk factors for nephrotoxicity occur-

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ring more acutely, as opposed to that developing after prolonged amphotericin B treatment. Finally, the retrospective nature of this study places limitations on accuracy, particularly with regard to those variables depending on faithful recordkeeping by health-care providers. Our study provides estimates of the risk of amphotericin B-associated nephrotoxicity as related to the average daily dose and its components. This information may be useful in assisting clinicians to determine how aggressively to pursue a course of antifungal therapy. Our study also has confirmed diuretic administration as an important, dose-dependent risk factor for nephrotoxicity during administration of amphotericin B. Diuretic use should be avoided if possible; if diuretics are necessary, they should be given with meticulous attention to intravascular volume status and, perhaps, in lower daily doses. Furthermore, patients with an abnormal serum creatinine level are at high risk of nephrotoxicity; whenever possible, such patients should be assessed and treated for potentially reversible causes of renal insufficiency prior to the initiation of amphotericin B treatment. Although aminoglycosides and other potentially nephrotoxic drugs have been postulated to contribute to amphotericin Bassociated nephrotoxicity, such relationships could not be confirmed in this study.

ACKNOWLEDGMENT We gratefully acknowledge and Ms. Hazel Price.

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REFERENCES 1. Butler WT. Bennett JE. Ailing DW. Wertlake PT, Utz JP. Hill GJ: Nephrotoxicity of amphotericin B. Early and late effects in 81 patients. Ann Intern Med 1964; 61: 175-187. 2. Medoff G, Kobayaski GS: Strategies in the treatment of systemic fungal infections. N Engl J Med 1980; 302: 145-155. 3. Butler WT. Hill GJ. Szwed CF. Knight V: Amphotericin B renal toxicity in the dog. J Pharmacol Exp Ther 1964; 143: 47-56. 4. Jose PA, Eisner GM Hollerman CE. Calcagno PL: Acute renal effects of amphotericln B. Proc Sot Exp Biol Med 1971; 137: 224-228. 5. Cheng J. Witty RT. Robinson RR, Yarger WE: Amphotericin B nephrotoxicity: increased renal resistanceand tubule permeability. Kidney Int 1982; 22: 626-633. 6. Gerkens JF. Branch RA: The influence of sodium status and furosemide on canine acute amphotericin B nephrotoxicity. J Pharmacol Exp Ther 1980; 214: 306-311. 7. Heidemann HT. Gerkens JF. Spickard WA, Jackson EK. Branch RA: Amphoteritin B nephrotoxicity in humans decreased by salt repletion, Am J Med 1983; 75: 476-481. 8. Bhathena DB. Bullock WE, Nuttall CE, Luke RG: The effects of amphotericin B therapy on the intrarenal vasculature and renal tubules in man. A studv of renal biops/es by light, electron, and immunofluorescence microscopy. Clin Nephrol 1978; 9: 103-110. 9. Weldon MW, Schultz ME: Renal ultrastructure after amphotericin B. Pathology 1974: 6: 191-200. 10. Burgess JL. Birchall R: Nephrotoxicity of amphotericin B, with emphasis on changes in tubular function. Am J Med 1972; 53: 77-84. 11. Feely J. Heidemann H, Gerkens J. Roberts LJ. Branch RAz Sodium depletion enhanced nephrotoxicity of amphotericin B (letter). Lancet 1981: I: 1422-1423. 12. Churchill DN. Seely J: Nephrotoxicity associated with combined gentamicinamphotericin B therapy. Nephron 1977; 19: 176-181. 13. Kisch AL, Maydew RP, Evan AP: Synergistic nephrotoxicity of amphoteticin B and cortisone acetate in mice. J Infect Dis 1978: 137: 789-794. 14. Cabrera J. Array0 V. Ballesta AM, et al: Aminoglycoside nephrotoxicity in cirrhosis. Gastroenterology 1982; 82: 97-105. 15. Stachling N. Sullivan KM: Fisher’s exact and Cornfield’s confidence intervals, version 1.0 1988 computer program (available from The Epidemiology Monitor). 16. Dixon WJ: BMDP statistical software. Berkley. California: University of Caliiornia Press. 1985; 330-343.

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