Medullary ischaemia in experimental analgesic nephropathy--the pathogenesis of renal papillary necrosis

Renal action of acute chloroquine and paracetamol administration in the anesthetized, fluid-balanced rat

Chloroquine induces diuresis, natriuresis, and an increase in glomerular filtration rate (GFR) in the rat. These responses are modified in rats with analgesic nephropathy induced by long-term paracetamol (acetaminophen) administration. Here, the effects of acute paracetamol treatment on renal function and the response to chloroquine are reported. Under intraval anesthesia (100 mg kg-1) male Sprague-Dawley rats (n = 6/group) were infused with 2.5% dextrose for 3 h. After a control hour, they received either vehicle, chloroquine (0.04 mg h-1), paracetamol (priming dose of 210 mg kg-1 followed by 110 mg kg-1h-1) or chloroquine and paracetamol over the next hour. Compared with vehicle, chloroquine infusion resulted in increases in GFR (2.4 +/- 0.3 versus 4.8 +/- 0.6 ml min-1), urine flow (4.2 +/- 0.3 versus 10.4 +/- 0.7 ml h-1), and sodium excretion (47.7 +/- 4.1 versus 171.2 +/- 18.6 micromol h-1) and a reduction in urine osmolality (223.2 +/- 5.9 versus 121.7 +/- 23.9 mOsM kg-1). Paracetamol reduced sodium excretion but had no effect on urine flow, GFR, or urine osmolality. When combined, paracetamol blocked the chloroquine-induced diuresis (3.9 +/- 0.7 ml h-1) and natriuresis (22.6 +/- 8.5 micromol h-1), attenuated the increase in glomerular filtration rate (3.5 +/- 0.2 ml min-1), and raised urine osmolality (280.0 +/- 22.8 mOsM kg-1). The differing effects of acute and long-term paracetamol treatment on basal and chloroquine-mediated renal function suggest that the length of prior exposure to paracetamol, and thus the presence of analgesic nephropathy, is an important determinant of the renal response to chloroquine.

Renal function in a rat model of analgesic nephropathy: effect of chloroquine

The antimalaria drug chloroquine is often taken against a background of analgesic nephropathy caused by nonsteroidal anti-inflammatory drugs such as paracetamol (acetaminophen). Chloroquine has marked effects on the normal kidney and stimulates an increase in plasma vasopressin via nitric oxide. The aim of this study was to determine the renal action of chloroquine in a model of analgesic nephropathy. Sprague-Dawley rats (n = 6-8/group) were treated with paracetamol (500 mg kg(-1) day(-1)) for 30 days in drinking water to induce analgesic nephropathy; control rats received normal tap water. Under intraval anesthesia (100 mg kg(-1)) rats were infused with 2.5% dextrose for 3 h to equilibrate and after a control hour they received either vehicle, chloroquine (0.04 mg h(-1)), N(omega)-nitro-L-arginine methyl ester (L-NAME, nitric-oxide synthase inhibitor, 60 micro g kg(-1) h(-1)) or combined chloroquine and L-NAME over the next hour. Plasma was collected from a parallel group of animals for vasopressin radioimmunoassay. Long-term paracetamol treatment resulted in a decrease in glomerular filtration rate (p < 0.05), sodium excretion (p < 0.001), and urine osmolality (p < 0.001), but no change in urine flow rate compared with untreated animals. Chloroquine administration in paracetamol treated rats induced a significant reduction (p < 0.05) in urine flow rate and a significant increase in plasma vasopressin (p < 0.001). These effects were blocked by coadministration of L-NAME and thus seem to be mediated by a pathway involving nitric oxide. However, these responses contrast with the chloroquine-induced diuresis previously observed in untreated rats, possibly reflecting paracetamol inhibition of renal prostaglandin synthesis and consequent moderation of vasopressin's action.

Combination analgesic-induced kidney disease: the Australian experience

Analgesic nephropathy is a unique drug-induced kidney disease characterized pathologically by renal papillary necrosis and chronic interstitial nephritis, and is the result of excessive consumption of combination antipyretic analgesics. The clinical features of the disorder relate mainly to the papillary necrosis, renal colic, and obstructive uropathy and the development of chronic renal failure in a small percentage of patients. There are significant geographic variations in the clinical features that may be related to the differing combinations of analgesics. The pathogenesis of the disease is in part related to the kidneys' ability to concentrate drugs in the papillae. The following sequence of events presents a plausible explanation for the evolution of the disease. If a combination of phenacetin and aspirin is ingested, the following steps occur. Phenacetin is converted in the gut and liver to acetaminophen by first-pass metabolism. Acetaminophen is then taken up by the kidney and excreted. During its excretion, acetaminophen becomes concentrated in the papillae of the kidney during physiologic degrees of antidiuresis, the concentration being up to five times the intracellular concentration of other tissues. Acetaminophen undergoes oxidative metabolism by prostaglandin H synthase to a reactive quinoneimine that is conjugated to glutathione. If acetaminophen is present alone, there is sufficient glutathione generated in the papillae to detoxify the reactive intermediate. If the acetaminophen is ingested with aspirin, the aspirin is converted to salicylate and salicylate becomes highly concentrated in both the cortex and papillae of the kidney. Salicylate is a potent depletor of glutathione. The mechanism is not completely understood; however, the inhibition of the production of NADPH via the pentose shunt is a possible explanation. With the cellular glutathione depleted, the reactive metabolite of acetaminophen then produces lipid peroxides and arylation of tissue proteins, ultimately resulting in necrosis of the papillae.

Caffeine potentiation of mefenamic acid-induced lesions in the rat renal medulla

The effect of caffeine given in combination with mefenamic acid on the renal medulla was examined. Sprague-Dawley rats were divided into four groups and gavage fed either vehicle suspension (control), mefenamic acid, mefenamic acid+caffeine or caffeine only for 4 months. Renal tissue taken from the corticomedullary junction was processed for electron microscopy. Ultrathin sections were cut after identification of vasa rectae on survey sections. On subsequent morphometric analysis, percentage interstitial tissue was calculated from the total area of vasa recta less the non-interstitial tissue. The median percentage of interstitial tissue in the mefenamic acid and caffeine group was 41 (range 33-50; n = 15) compared with 34 (20-48; n = 20) in mefenamic acid (P less than 0.01), 29 (15-42; n = 15) in caffeine only (P less than 0.001) and 32 (20-46; n = 18) in vehicle-treated animals (P less than 0.001). There were no significant differences between mefenamic acid alone and vehicle or caffeine-only groups or between caffeine-only and vehicle-treated controls. This suggests that caffeine potentiates the effect of the non-steroidal anti-inflammatory drug, mefenamic acid, on the rat renal medulla, resulting in a quantitative increase in the interstitial tissue between adjacent afferent and efferent vasa recta.

Aspirin, paracetamol and non-steroidal anti-inflammatory drugs. A comparative review of side effects

Non-steroidal anti-inflammatory drugs (NSAIDs) effectively control the symptoms of many of the rheumatic diseases although they have little effect on the underlying causes. Their effect is mainly on the mediators of the inflammatory process. Unfortunately, these mediators have important physiological roles in the maintenance of health, particularly in the gastrointestinal tract and the kidney, so that their inhibition results in many unwanted reactions of varying severity. The mechanisms underlying these reactions are described. Their occurrence varies, both qualitatively and quantitatively, and an attempt is made to assess these differences, although it may be that they are related directly to differences in dosage and therapeutic efficacy. In addition, immunologically mediated adverse reactions occur. These mechanisms are outlined and related to the clinical picture. There are considerable differences in frequency of reactions between the compounds: in particular there is a wide variation in the rate of dermatological reactions of this type. Agranulocytosis has been particularly associated with the pyrazolone compounds, although it has been reported with most others. Aplastic anaemia, which may not be an immune-mediated reaction, is also thought of as a pyrazolone reaction, but the incidence with indomethacin approaches a similar level. Although all drugs analysed may cause hepatic reactions, these are rare except with the now withdrawn benoxaprofen. Several types of immunologically mediated renal reactions occur and these rarities are also described. Paracetamol does not have any effect on the inflammatory mediators. Anxieties about this substance relates to the parent compound phenacetin and its necrotic effect on the renal papillae. There is extensive literature on this subject concerning not only paracetamol, but also aspirin and other NSAIDs. This is also assessed and summarised. The danger of paracetamol as a direct hepatic toxin in self-poisoning is discussed. Novel NSAIDs are introduced and others withdrawn with frequent and monotonous regularity. Sometimes the reasons have some medical or scientific plausibility, but often they are over-reactions by registration authorities or pharmaceutical companies in response to uninformed media publicity. The problems of the numerically and scientifically accurate collection and assessment of adverse reaction data are legion and as a result useful agents have been lost. Some of these difficulties are described, and some non-drug 'adverse reactions' are described.(ABSTRACT TRUNCATED AT 400 WORDS)

Analgesic-associated nephropathy

Although the question of whether or not analgesic abuse leads to a certain type of nephropathy has been investigated since 1953, no conclusive answer has been forthcoming. Epidemiologic investigations on the correlation between analgesic abuse and renal function as well as experimental animal studies have given contradictory results concerning the possibility of analgesic-associated kidney damage. However, studies on the correlation between analgesic abuse and papillary necrosis have demonstrated that this lesion coincides in 69% of the cases with an analgesic history. Follow-up studies of patients with analgesic nephropathy have shown that renal function deteriorates in 60% of the patients with continued abuse and that it stabilizes in 80% of the patients after cessation of abuse. Studies on the legislative restriction of phenacetin/acetaminophen, carried out mostly in Scandinavian countries since 1965, show a 50%-90% decline in signs of analgesic nephropathy (papillary necrosis) following a reduction in the sale of these drugs. The prevalence of analgesic abuse may be underestimated, since up to 80% of the abusers tend to deny their analgesic intake. Obviously, only a small percentage of analgesic abusers (approximately 1%) finally develop nephropathy. Even though the results of epidemiologic and experimental studies are contradictory, the results of investigations on papillary necrosis and on legislative prevention as well as of patient follow-ups tend to indicate a correlation between analgesic abuse and a well-defined type of nephropathy.

Renal effects of antipyretic analgesics

Most antipyretic analgesics can cause acute nephrotoxic effects, including acute tubular necrosis, acute interstitial nephritis, glomerular toxicity, and functional changes, such as "salicyl edema," following large doses of sodium salicylate. Most functional changes are related to acute suppression of prostaglandin synthesis, "the acute prostaglandin-effect," and have been primarily noted with the use of indomethacin. The association between prolonged and excessive consumption of compound analgesics and the development of renal disease and renal failure, characterized by renal papillary necrosis, is now well established. Studies in several countries have shown that the incidence of analgesic nephropathy as an indication for dialysis and transplantation corresponds to the per capita consumption of phenacetin in compound analgesics. Analgesic nephropathy, which is part of a wider clinical syndrome, the analgesic syndrome, is uncommon following the use of single analgesics. Analgesic nephropathy and the analgesic syndrome are discussed in detail, including the development of uroepithelial tumors.

Renal medullary crest necrosis associated with phenylbutazone therapy in horses

Thirty-five cases of renal medullary crest necrosis morphologically similar to the renal papillary necrosis of analgesic nephropathy as described in man and rats are reported in horses receiving maintenance dosages of phenylbutazone. The primary lesion is a well-demarcated focal medullary necrosis resulting in sequestration of fragments of the renal crest. Renal cortical lesions are considered secondary to the medullary necrosis and consist of segmental pallor as a result of tubular dilatation, filtrate retention, and interstitial edema. Ischemia in concert with phenylbutazone is suggested as the etiology. Renal medullary crest necrosis is presented as more appropriate morphological terminology for this lesion in the equine species than renal papillary necrosis as is used in man and rats.

Aspirin and renal disease

Historic data has suggested a relationship between aspirin ingestion and the subsequent occurrence of renal papillary necrosis. In most case reports, analgesic mixtures containing aspirin, phenacetin, and caffeine were taken. This resulted in the term "analgesic nephropathy." In clinical studies, phenacetin has been the major common denominator, whereas experimental data in rats implicate aspirin as the major nephrotoxin. Except with massive doses, attempts at producing nephrotoxicity in laboratory animals with phenacetin have failed; however, a high proportion of rats fed aspirin alone have developed renal papillary necrosis. Acute reversible effects of aspirin on renal function in patients with active lupus nephritis have been demonstrated. Data are presented in 46 patients who took aspirin continuously for 10 or more years (mean total dosage 35 kg) in whom there was no evidence of significant renal dysfunction. These data suggest that, while aspirin may cause minor histologic or functional renal abnormalities, it is unlikely that long-term salicylate consumption causes serious renal disease.

Antagonism between non-steroidal anti-inflammatory drugs and diuretics

Renal osmolal clearance after a standard water load was measured in healthy volunteers. After flurbiprofen, 100 mg by mouth, the osmolal clearance fell by 29 per cent. After frusemide, 40 mg by mouth or 20 mg intravenously, the osmolal clearance increased by 105 per cent and 140 per cent respectively, but following pre-treatment with flurbiprofen, the corresponding increases in osmolal clearance were only 19 per cent and 70 per cent. The antagonism between non-steroidal anti-inflammatory drugs and diuretics, of which this is an example, may be a common and clinically important drug interaction.

[Toxic nephropathies (author's transl)]

Direct tubular damage, hypersensitivity reaction, metabolically mediated kidney disturbances, and chronic nephropathies are important sequelae of several drugs or their metabolites. In this review the drug-induced kidney disease is discussed from a clinical, histological, and pathogenetic point of view. The knowledge of possible nephrotoxic reactions and their underlying toxins are essential for prevention of this kidney disease.

Clinical and pathological aspects of analgesic nephropathy

1 Analgesic nephropathy is part of the analgesic syndrome which has gastrointestinal, haematological, cardiovascular, psychological and psychiatric, and pregnancy and gonadal manifestations; premature ageing may also be a feature. 2 Analgesic nephropathy is a form of renal disease characterized by renal papillary necrosis, secondary chronic interstitial nephritis and renal failure with features of predominant tubulointerstitial dysfunction. 3 The percentage of patients with analgesic nephropathy who present with terminal renal failure is 12%. With appropriate management, 17% of analgesic nephropathy patients improve, 50% remain stable and 23% deteriorate. The 6 year cumulative survival is 70%. The major factors influencing deterioration are malignant hypertension, persistent proteinuria and small initial renal size. 4 The risk of renal papillary carcinoma in patients who regularly take analgesics is 8 per 100,000 patients per year. 5 Renal papillary necrosis is a consequence of the chronic toxicity of all non-steroidal anti-inflammatory drugs and results from medullary ischaemia secondary to suppression of prostaglandin E2 synthesis and from direct cellular toxicity. 6 Analgesic nephropathy is a preventable form of renal disease and renal failure. It can be prevented by limiting the abuse potential of analgesics rather than by making minor modifications in the composition of analgesic mixtures.

[Prostaglandins in cardiovascular and renal function. Biochemical, physiological and clinical findings (author's transl)]

Prostaglandins (PG) are highly unsaturated, cyclic fatty acids with 20 carbon atoms which are biosynthesized from dihomo-gamma-linolenic, arachidonic and eicosapentaenoic acids. These fatty acids are either ingested or are biosynthesized from linoleic and linolenic acids, respectively. The PG-precursor fatty acids are liberated from membrane phospholipids by phospholipase A and are converted to prostaglandins by the multienzyme complex PG-synthetase. The activity of the PG-system is influenced by extracellular hormonal, neural and mechanical stimuli and by intracellular factors such as ion-concentration and activity of the enzymes adenyl- and guanylcyclase. Prostaglandins are tissue hormones or autacoids which act on their receptors near their site of synthesis and degradation. The prostaglandin family constitutes a group of more than 10 natural occurring compounds showing a variety of biological actions. In arteries and veins the different PG:s have vasodilating as well as vasoconstricting effects. In addition, they are involved in the regulation of vascular smooth muscle proliferation. Within the kidney PG:s have vascular and tubular actions. They antagonize the effect of ADH, mediate renin secretion and are involved in the control of electrolyte balance. In the regulation of platelet aggregation and platelet adhesion PG:s have opposite functions: Prostacyclin which is synthesized in the vascular wall antagonizes the aggregating action of Thromboxane A2 which is formed in the platelets. A defect or an imbalance in the production of PG:s in the vascular wall, in platelets or in the kidney is assumed to play a pathogenetic role in a variety of cardiovascular and renal diseases such as in hypertension, atherosclerosis, persistent ductus arteriosus and Bartter's syndrome.

Renal papillary necrosis associated with indomethacin and phenylbutazone treated rheumatoid arthritis

A case of renal papillary necrosis is reported in a 55-year-old man with rheumatoid arthritis. He consumed 1.1 kg indomethacin and 5.5 kg phenylbutazone over the seven years prior to presentation.

Pharmacological mechanisms of analgesic nephropathy

The situation in the experimental field is unresolved; too many factors require clarification before the critical experiment can be conducted to settle the matter once and for all. However, as there is now plentiful evidence to convince any reasonable physician that commonly available analgesics, when abused, carry a significant health risk, one may resonably ask whether any further experimental evidence is needed? The object of this review is in no sense divisive, i.e., by pointing out discrepancies in the available data to thereby cloud the issue rather than resolve them. The problem of abuse lies properly in the field of public health education, and the first step to this would surely be an appropriate worning on the packaging of all commonly used analgesics. For future research, however, government health authorities should be guided in their preclinical testing requirements for mild antiinflammatory analgesics, and enough is now known to draw up guidelines for good laboratory practice in this field.

Experimental renal papillary necrosis

Review of experimental work indicates that renal papillary necrosis (RPN) is more readily induced by mixtures of analgesics which include phenacetin or paracetamol, than by either of the latter drugs alone. In an experiment in which moderate doses of analgesics were given to rats over a long period, it was shown that aspirin had a greater nephrotoxic effect than either phenacetin or paracetamol although less than in combination with either. In a study of the evolution of aspirin-induced damage, the earliest changes were shown to occur in the interstitial cells. There was also loss of medullary mucopolysaccharides. Occlusive lesions were demonstrated in the vasa recta. Using partial papillectomy, it was shown that the development of analgesic-induced cortical lesions did not depend on the presence of papillary necrosis. It was suggested that the early papillary changes might be due to ischemia, medullary blood flow being reduced as a result of aspirin's action as an inhibitor of prostagladin synthesis. The lesions in the vasa recta might cause ischemia at a late stage, leading to total RPN.

Analgesic nephropathy: etiology, clinical syndrome, and clinicopathologic correlations in Australia

Analgesic abuse is a major public health hazard in Australia, and analgesic nephropathy with consequent terminal renal failure is the underlying cause in 20% of the patients requiring dialysis and transplantation. Analgesics are invariably taken in the form of compounds and mixtures. In the aspirin-phenacetin-caffeine (APC) mixture, aspirin appears to be the major nephrotoxic agent and phenacetin appears to play a secondary and synergistic role. The renal disease associated with abuse of analgesics is characteristic and is part of a much wider clinical syndrome, the analgesic syndrome, which includes peptic ulcer disease (35%), anemia (60 to 90%), hypertension (15 to 70%), ischemic heart disease (35%), psychological and psychiatric manifestations, pigmentation, and possible gonadal- and pregnancy-related effects. The primary lesion in analgesic nephropathy is renal papillary necrosis (RPN), and this is a nephrotoxic effect common to all nonsteroid antiinflammatory agents. The most important factor in the management of patients with analgesic nephropathy is the cessation of analgesic abuse, and this leads to improvement and stabilization of renal function. A small proportion of patients will, however, deteriorate in relation to accelerated hypertension, persistent proteinuria, ischemic heart disease, and complications leading to nephrectomy. Patients with analgesic nephropathy are poor risk patients and have a poor prognosis, even after dialysis and transplantation.

Aspirin, phenacetin, and the kidney: a rheumatism clinic study

In a rheumatism clinic study in Brisbane, the consumption of aspirin and phenacetin compounds (APC) containing more than one kilogram of aspirin and phenacetin was significantly associated with overt renal papillary necrosis (RPN) and with a renal score, but when more than one kilogram of aspirin was taken without phenacetin there was no such association. Analysis and comparison with the parallel New Zealand study showed an overall risk of RPN of at least 10-6% when more than one kilogram of aspirin was taken in APC form, and 0-3% when aspirin was taken without phenacetin. An additive interaction of phenacetin and aspirin is postulated. It is concluded that phenacetin use should be severely restricted.

Association of renal papillary necrosis and ankylosing spondylitis

Three patients with ankylosing spondylitis developed renal papillary necrosis. All had received prostaglandin synthetase inhibitors including phenylbutazone, indomethacin, or ibuprofen. One patient had sickle trait. These drugs are not commonly associated with papillary necrosis in man, but may adversely effect renal medullary blood flow. An underlying renal vascular abnormality related to ankylosing spondylitis is also considered. Patients with ankylosing spondylitis who are taking prostaglandin synthetase inhibitors should be routinely screened for hematuria.

Analgesic abuse and kidney disease

The analgesic syndrome, comprising renal disease, hypertension, peptic ulcer, anaemia and recurrent headache, accounts for wide-spread morbidity and mortality especially in Queensland and New South Wales. Epidemiological and clinical evidence gathered from many Western societies implicates unsupervised consumption of compound analgesic preparations, particularly those containing phenacetin, in the causation of the majority of cases. Laboratory experiments so far have failed to produce an entirely satisfactory model of clinical analgesic nephropathy. In small animals, papillary necrosis results from prolonged feeding with large doses of aspirin and a number of other anti-inflammatory agents more readily than when phenacetin, paracetamol or phenazone is given alone. The apparently conflicting deductive and experimental data may be reconciled if, as indicated by preliminary observations, salicylates enhance the toxicity of phenacetin derivatives. In planning a programme of prevention for the analgesic syndrome, the central aetiological role of non-narcotic drug dependency must be recognized. As the analgesics to which addiction commonly occurs are the compound powders and tablets, or those containing a stimulant, these preparations should be available only in circumstances where their use can be monitored. Suspected unsupervised and unwarranted consumption of analgesics should be checked by urinary testing for drug metabolites. Because the underlying problem of analgesic dependency is behavioural and environmental in origin rather than medical, the physician must combine forces with the social engineer to devise a definitive solution for this condition.

Aspirin damage in the rat kidney in the intact animal and after unilateral nephrectomy

Aspirin caused epithelial hyperplasia, papillary necrosis with calcification and cortical changes in the rat kidney. After unilateral nephrectomy the lesions appeared more rapidly and were more severe. In the electron microscope the earliest changes were observed in the interstitial cells.

Papillary necrosis in renal allografts--report of 2 cases

Two patients are reported in whom early and irreversible renal allograft rejection was associated with passage of necrotic papillary material in the urine. Evidence is presented for a causal relationship between rejection and medullary necrosis. Passage of a papilla is regarded as a definite indication for graft exploration.