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Etiology

Continued analgesic abuse was associated with deterioration in renal function in patients with analgesic nephropathy

ACP J Club. 1991 May-June;114:90. doi:10.7326/ACPJC-1991-114-3-090


Source Citation

Hauser AC, Derfler K, Balcke P. Progression of renal insufficiency in analgesic nephropathy: impact of continuous drug abuse. J Clin Epidemiol. 1991 Jan;44:53-6.


Abstract

Objective

To determine whether patients with analgesic nephropathy and progressive renal dysfunction, who denied having continuing analgesic abuse, were more likely to have objective evidence of continuing analgesic use than similar patients without further deterioration of renal function.

Design

Case-control study.

Setting

Outpatient clinic in Austria.

Patients

23 patients with analgesic nephropathy were studied. The diagnosis was based on history of long-term intake of phenacetin or acetaminophen > 3.5 kg, sonography, intravenous pyelography, with renal biopsy in uncertain cases. All patients denied continuing analgesic use. In the preceding year, 12 of 23 patients (group 1: mean age 55 years, 9 women) showed no deterioration of kidney function (rise in creatinine < 10% over baseline), whereas 11 patients (group 2: mean age 63.5 years, all women) showed deterioration. Patients in group 1 were considered to be case patients and patients in group 2 were considered to be control patients.

Assessment of risk factors

Blood samples for acetaminophen and salicylate were drawn at a routine follow-up visit, with simultaneous patient consent. Assays measured parent drug substances, the half-lives of which are not prolonged by renal failure.

Main outcome measure

Increases in serum creatinine level over the preceding year.

Main results

In group 1 the mean serum creatinine level was 2.74 mg/dL (upper limit of 95% CI 4.9) at the start of the study and 2.76 mg/dL (upper limit CI 5.1) after 1 year. In group 2, the mean serum creatinine level rose from 3.86 (upper limit CI 7.1) to 6.40 (upper limit CI 12.7, P < 0.01). Acetaminophen was present in blood test results for 2 of 12 patients (17%) in group 1 and 9 of 11 patients (82%) in group 2 (P < 0.01 for the difference between the 2 groups). Salicylate was present when acetaminophen was present but not at other times. When confronted with positive test results, 6 patients admitted regular drug intake (daily dose ranging from 400 to 800 mg for acetaminophen and from 500 to 1000 mg for salicylate), 4 patients admitted irregular intake, and 1 denied intake. Headache was the most common cause of drug abuse.

Conclusion

Continuing analgesic abuse was frequent among patients with analgesic nephropathy, was hidden from clinical staff, and was associated with deterioration in renal function.

Source of funding: Not stated.

Address for article reprint: Dr. P. Balcke, 1st Medical Clinic, University of Vienna, Lazarettg 14, 1090 Vienna, Austria.


Commentary

Hauser and colleagues found that 82% patients with analgesic nephropathy whose renal function had deteriorated in the preceding year were ingesting analgesics, whereas only 17% of patients with stable renal function were doing so. These data complement earlier prospectively obtained evidence that the prognosis of analgesic nephropathy is good if analgesic ingestion ceases and poor if it does not (1).

Is drug-induced renal deterioration as prevalent in other patients with analgesic nephropathy? It would help to know whether recruitment into this study was affected by the willingness of patients to submit to testing or by unspoken suspicions of physicians about selected persons. Were patients with declining function disproportionately represented because of closer follow-up?

The authors state that all detected users of analgesics had previously concealed their ingestion. Why did continuing abusers voluntarily permit testing that was destined to expose their behavior? Were they hoping to be discovered?

The results of this case-control study suggest that clandestine analgesic abuse plays a role in most unexplained deterioration of renal function in patients with analgesic nephropathy. As has been previously suggested (2), it cannot harm and may help these patients to test and counsel them accordingly.

Kenneth R. Phelps, MD
Albany Medical CenterAlbany, New York, USA


References

1. Gault MH. The clinical course of patients with analgesic nephropathy. Can Med Assoc J. 1975;113:204-7.

2. Gault MH, Wilson DR. Analgesic nephropathy in Canada: clinical syndrome, management, and outcome. Kidney Int. 1978;13:58-63.


Author's Response

All our patients with analgesic nephropathy were included in this study, all were tested, and both groups of patients were followed equally closely. Thus, willingness to submit to testing or suspicions about selected persons did not play a role.

We believe that the patients were hoping that the drug abuse would not be detected. The amount of analgesics ingested might also have been smaller than previously and considered negligible by the patient.

P. Balcke