Drug-drug and drug-disease interactions with nonsteroidal anti-inflammatory drugs

Use of NSAIDs in treating patients with arthritis

Patients with rheumatic diseases, including rheumatoid arthritis and osteoarthritis, almost universally describe pain and stiffness as important contributors to reduced health-related quality of life. Of the treatment options available, NSAIDs are the most widely used agents for symptomatic treatment. NSAIDs are effective anti-inflammatory and analgesic drugs by virtue of their ability to inhibit biosynthesis of prostaglandins at the level of the cyclooxygenase enzyme. However, many of the adverse effects of NSAIDs are also related to inhibition of prostaglandin production, making their use problematic in some patient populations. For the clinician, understanding the biology of prostaglandin as it relates to gastrointestinal, renal, and cardiovascular physiology and the pharmacologic properties of specific NSAIDs is key to using these drugs safely. Of particular importance is the recognition of co-morbid conditions and concomitant drugs that may increase the risk of NSAIDs in particular patients. In patients with risk factors for NSAID toxicity, using the lowest dose of a drug with a short half-life only when it is needed is likely to be the safest treatment option. For those patients whose symptoms cannot be managed with intermittent treatment, using protective strategies is essential.

Symmetric dimethyl arginine and N-acetyl-β-D-glucosaminidase lysozimuria of proximal renal tubules as a target for nephrotoxicity in patients with rheumatoid arthritis treated with disease modifying antirheumatic drugs

BACKGROUND

The aim of this study was to determine the effect of initial therapy with some disease modifying antirheumatic drugs (DMARDs) (Methotrexate and Ketoprofen) on glomerular and tubular integrity in patients with Rheumatoid arthritis (RA).

OBJECTIVES

OBJECTIVES

To determine whether there is a change in clinical and laboratory indicators of renal function in course of the follow up of treatment and whether that change correlates with the dynamics of the quantity of enzymes excreted in urine and reactants of the acute phase.

MATERIALS AND METHODS

Using colorimetric method for determination of NAG, samples of 70 participants were examined (35 RA patients treated with Ketoprofen only, 35 RA patients treated with combined use of Methotrexate and Ketoprofen). The follow up was 5 time-intervals in the course of 24 weeks.

RESULTS

There was moderate correlation between NAG and microalbuminuria (r=0,34) in the group of patients treated with Ketoprofen only, while statistically significant correlation (r=0,21) was seen in group of patients with combined use of Methotrexate and Ketoprofen. NAG enzymuria in size, number of patients registered, and time of appearance were greater and appears earlier in the group with the combined use of Methotrexate and Ketoprofen compared with the mono-therapy with Ketoprofen. Mean urinary NAG induction was increasing with the concomitant use of Methotrexate and Ketoprofen.

CONCLUSIONS

Methotrexate is more potent NAG inductor than Ketoprofen and provokes greater tubular enzymuria than Ketoprofen.

The anti-inflammatory non-antibiotic helper compound diclofenac: an antibacterial drug target

Diclofenac sodium (Dc) was found to possess antibacterial activity against both drug-sensitive and drug-resistant clinical isolates of Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, and Mycobacterium spp., in addition to its potent anti-inflammatory activity. The time-kill curve study indicates that this non-steroidal drug exhibits bactericidal activity against Listeria, E. coli, and M. tuberculosis. The antibacterial activity of Dc comes, in part, from its ability to inhibit the DNA synthesis of E. coli and L. monocytogenes. Dc could protect murine listeriosis, salmonellosis, and tuberculosis at doses ranged within its maximum recommended human or non-toxic ex-vivo dose. Dc possesses anti-plasmid activity and acts as a 'helper compound' in synergistic combination with streptomycin against E. coli and Mycobacterium or gentamicin against Listeria. This review focuses on the possible use of Dc, a non-antibiotic helper compound, in infections and inflammatory conditions, rationalized on the basis of the activities of the compounds.

The influence of cardiovascular and antiinflammatory drugs on thiazide-induced hemodynamic and saluretic effects

OBJECTIVE

Thiazide diuretics are known to induce a transient fall of the glomerular filtration rate (GFR), which, in turn, reduces tubular Na(+) load. This tubuloglomerular feedback (TGF) curtails the natriuretic effect of this class of diuretics. Cardiovascular and antiinflammatory therapeutics may interfere with TGF and thereby influence the effect of thiazides once co-administration is clinically indicated.

METHODS

The effects on GFR and saluresis of hydrochlorothiazide (HCT; 25 mg) monotherapy were measured in healthy volunteers and compared to those obtained during co-administration of the thiazide and a second therapeutic.

RESULTS

In the presence of the ACE inhibitor enalapril (10 mg), the transient fall in the GFR induced by HCT was almost abolished, and Na(+) excretion increased by approximately 30 % as compared to HCT monotherapy. K(+) excretion, however, remained unchanged. Similar results were obtained with the AT II type 1 receptor antagonist candesartan (8 mg): GFR remained stable, Na(+) excretion rose by 35 % and K(+) excretion was not changed. The effect of the Ca(2+) channel blocker amlodipine (5 mg) on GFR and HCT-induced Na(+) excretion equalled that obtained with the AT(1) blocker, yet with this treatment K(+) excretion rose in proportion to Na(+) excretion. The beta-blockers propranolol (80 mg) or bisoprolol (5 mg) reduced GFR but maintained TGF. HCT-induced Na(+) excretion was significantly reduced in the presence of a beta-blocker, whereas K(+) excretion was not changed. The inhibition of cyclooxygenase by diclofenac (50 mg) or rofecoxib (25 mg) significantly reduced the diuretic/natriuretic effect of HCT, but K(+) excretion was unchanged, and TGF was still demonstrable.

CONCLUSION

In conclusion, AT(1) receptors, as well as the Ca(2+) channels in the smooth muscle cells of the afferent arteriole, are considered prerequisites for TGF function; their blockade increases the diuretic/natriuretic efficacy of thiazide diuretics. In contrast, beta-blockers and COX inhibitors do not interfere directly with TGF. These first dose effects reflect the primary response of the kidney to the drugs. They cannot, however, predict the benefits of long-term treatment.

Choosing the right nonsteroidal anti-inflammatory drug for the right patient: a pharmacokinetic approach

Effective use of the growing number of nonsteroidal anti-inflammatory drugs (NSAIDs), a group that has recently been augmented by the introduction of the selective cyclo-oxygenase-2 inhibitors, requires adequate knowledge of their pharmacokinetics. After oral administration, the absorption of NSAIDs is generally rapid and complete. NSAIDs are highly bound to plasma proteins, specifically to albumin (>90%). The volume of distribution of NSAIDs is low, ranging from 0.1 to 0.3 L/kg, suggesting minimal tissue binding. NSAID binding in plasma can be saturated when the concentration of the NSAID exceeds that of albumin. Most NSAIDs are metabolised by the liver, with subsequent excretion into urine or bile. Enterohepatic recirculation occurs when a significant amount of an NSAID or its conjugated metabolites are excreted into the bile and then reabsorbed in the distal intestine. NSAID elimination is not dependent on hepatic blood flow. Hepatic NSAID elimination is dependent on the free fraction of NSAID within the plasma and the intrinsic enzyme activities of the liver. Renal elimination is not an important elimination pathway for NSAIDs, except for azapropazone. The plasma half-life of NSAIDs ranges from 0.25 to >70 hours, indicating wide differences in clearance rates. Hepatic or renal disease can alter NSAID protein binding and metabolism. Some NSAIDs with elimination predominantly via acylglucuronidation can have significantly altered disposition. Pharmacokinetics are also influenced by chronobiology, and many NSAIDs exhibit stereoselectivity. There appear to be relationships between NSAID concentration and effects. At therapeutically equivalent doses, NSAIDs appear to be equally efficacious. The major differences between NSAIDs are their therapeutic half-lives and safety profiles. NSAIDs undergo drug interactions through protein binding displacement and competition for active renal tubular secretion with other organic acids. When choosing the right NSAID for the right patient, individual patient-specific and NSAID-specific pharmacokinetic principles should be considered.

Inhibition of haloperidol reduction by non-steroidal anti-inflammatory drugs in human liver cytosol

A thorough knowledge of drug-drug interactions is crucial as the practice of multiple drug therapy escalates. In vitro studies using human liver enzymes are a valuable and non-invasive tool for predicting potential drug interactions in vivo. 1. A simple radio-TLC method was developed to monitor the formation of reduced haloperidol from haloperidol in human liver cytosol. 2. Indomethacin, known to be a potent inhibitor of 3a-hydroxysteroid dehydrogenase, was chosen as a reference for the evaluation of several arylpropionic acid derived non-steroidal anti-inflammatory drugs, ketoprofen, tiaprofenic acid, fenbufen, Ibuprofen, d-naproxen and 1-naproxen. The IC₅₀ ranged from 0.4-6.0 mM with indomethacin the most potent inhibitor of haloperidol carbonyl reductase. 3. The carbonyl reduction of haloperidol was inhibited significantly by these most commonly used non-steroidal anti-inflammatory drugs and the degree of inhibition reflected their pharmacological potency. 4. Sephadex G-100 fractionation of human liver cytosol yielded a fraction with haloperidol reductase activity at a molecular weight of about 32,000.

Influence of meloxicam on furosemide pharmacokinetics and pharmacodynamics in healthy volunteers

Fifteen healthy male volunteers participated in an open, multiple-dose study to investigate a possible interaction between furosemide and meloxicam, a new non-steroidal anti-inflammatory agent (NSAID). The study comprised three treatment periods. First, furosemide (40 mg) was administered as a single oral daily dose for 3 days. A wash-out day was followed by the administration of meloxicam (15 mg) as a single oral daily dose for 10 days. Thereafter, meloxicam and furosemide were administered concomitantly at the same doses as described above, for 3 days. The effect of concomitant ingestion of meloxicam and furosemide on furosemide-induced diuresis, urine and serum electrolytes, and furosemide pharmacokinetics was determined, after both single and repeated administration of furosemide. Estimates of the "(furosemide+meloxicam)/(furosemide alone)" mean ratio of the variable AUC(0-infinity) for plasma furosemide and the cumulative sodium excretion (0-8 h) were 97.4% (90% confidence interval 89.7-106%) and 88% (90% confidence interval 82-94%), respectively. The study results indicate that meloxicam does not affect the pharmacokinetics of furosemide in healthy volunteers, nor does it affect furosemide-induced diuresis or serum electrolytes. The cumulative urinary electrolyte excretion after concomitant administration of meloxicam and furosemide is somewhat lower than after administration of furosemide alone, in particular for the period 0-8 h after administration of furosemide. This effect of meloxicam on furosemide dynamics is small, and is probably not clinically relevant in healthy volunteers under the dosing regime studied.

Effect of tenidap sodium on the pharmacodynamics and plasma protein binding of warfarin in healthy volunteers

1. An open-label, randomised study was performed to assess the effect of tenidap sodium on the pharmacodynamics and plasma protein binding of warfarin. 2. Fourteen healthy male volunteers received either a single oral dose of 120 mg tenidap sodium or matching placebo capsules from days 11 to 36. A single oral dose of 0.75 mg kg-1 warfarin was administered on days 1 and 32. 3. The mean prothrombin AUC(1,120h) value between baseline and day 32 increased from 1692.4 +/- 234.5 s h to 1769.3 +/- 218.0 s h in the group given tenidap, and decreased from 1747.6 +/- 289.4 s h to 1708.1 +/- 236.8 s h in the placebo group. 4. Tenidap caused a slight delay in the normalisation of prothrombin times following the second dose of warfarin on day 32 compared with the first dose on day 1. This was significant at 36, 48, 72 and 96 h but not at 120 h after administration of warfarin. 5. The mean percentage of unbound warfarin in the tenidap group (0.08% +/- 0.09) was significantly different (P = 0.047) from that in the placebo group (-0.03% +/- 0.10) but this was not considered to be clinically meaningful. 6. These data indicate that prothrombin times should be monitored during concomitant administration of tenidap and warfarin.

Effects of diclofenac on isradipine pharmacokinetics and platelet aggregation in volunteers

In this open, two-period crossover study in 18 healthy male volunteers, a single oral dose of 50 mg diclofenac was administered alone and on day 7 of multiple oral dosing of 5 mg b.i.d. isradipine to assess a possible pharmacokinetic interaction. The effect of these drugs on ex vivo platelet function was also determined. Serial blood samples were obtained over 12-hour periods on three occasions: after the single diclofenac dose; after the morning dose of isradipine on day 6 and after co-administration of both drugs on day 7 of steady-state isradipine administration. Additional samples were taken at 2 h post dose for determination of ex vivo platelet aggregation. Isradipine plasma concentrations were determined by a gas chromatographic method and diclofenac plasma concentrations by an HPLC method. The pharmacokinetic characteristics of diclofenac were unaltered during co-administration. The maximum plasma concentration of isradipine was increased 19.6% during co-administration from 5.06 to 6.05 ng.ml-1. This is not expected to be of clinical importance. Isradipine's apparent total body clearance and steady-state AUC remained unchanged. Ex vivo induced platelet aggregation was not affected by any of the treatments.

Renal effects of nimesulide in furosemide-treated subjects

In clinical settings where effective plasma volume is decreased, nonsteroidal anti-inflammatory drugs (NSAIDs) may induce acute renal failure. We have evaluated the effects of single and repeated doses of nimesulide on renal haemodynamics and electrolyte excretion in 8 healthy volunteers during a prolonged course of furosemide (frusemide). Under these study conditions, renal prostaglandin synthesis is expected to be elevated, with renal function being dependent upon increased levels of prostaglandins. Nimesulide induced an acute but transient decrease in indices of renal haemodynamics. Furosemide-induced increases in plasma renin activity and aldosterone levels were blunted, and urinary excretion of prostaglandin E2 was markedly reduced by nimesulide. The magnitude and time course of the natriuretic, kaliuretic and diuretic effects of furosemide were attenuated by nimesulide. Although the transient nature of the observed renal haemodynamic changes suggests that the risk of developing acute renal failure is small, the rise should be taken into account in patients with renal dysfunction. Sodium and potassium retention, and the blunting of the diuretic-induced electrolyte excretion, could be of clinical relevance. Nimesulide appears, therefore, to share the prostaglandin-dependent renal effects of other NSAIDs.

Steady state pharmacokinetic profile of indomethacin in elderly patients and young volunteers

The steady-state pharmacokinetic profile of indomethacin was examined in twelve healthy volunteers (4 m, 8 f; 20-34 y) and in 12 elderly subjects (7 m, 5 f; 70-88 y). Two formulations of indomethacin were examined, providing duplicate data for each subject group. The subjects received each formulation of indomethacin (25 mg tid) for 6 days in a single blind crossover fashion. On day 7, after an overnight fast, a final 25 mg dose of indomethacin was given and plasma concentrations measured over the following 12 h. Kinetic parameters Cpmin, Tmax and AUC (0-12 h) were determined. There were no differences in the pharmacokinetic parameters between young and elderly subjects or between data for the two formulations of indomethacin. AUC values (micrograms.ml-1.h), for example, for the two formulations in the young subjects were 5.85 and 6.85 while the values for the elderly subjects were 6.55 and 6.50 respectively. When each treatment period was considered independently there was a significant difference between young and elderly subjects with regard to compliance. The rates of non compliance (over and under compliance) using a capsule count technique were, however, low with a mean maximum value of 5.8% being recorded for the elderly subjects.

A comparison of synovial fluid concentrations of non-steroidal anti-inflammatory drugs with their in vitro activity

For NSAIDs it has been widely accepted that prostaglandin inhibition is their mechanism of action in clinical use. Yet many other actions have been described, although it is unclear to what extent these may contribute to clinical activity. This review attempts to relate some of the experimental activities of NSAIDs to concentrations of drugs which occur in clinical use. Since it is assumed that to be effective a drug must reach its target site of action, synovial fluid concentrations for NSAIDs are considered. The resulting analysis suggests that prostaglandin inhibition is a viable mode of action for most, if not all, NSAIDs. However, some NSAIDS may rely as much, if not more, on other actions for their anti-inflammatory effect.

Nonsteroidal anti-inflammatory drug toxicity: increased risk in the elderly

Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used in the therapy of rheumatic diseases, especially in older patients. The toxicity profile of NSAIDs includes gastrointestinal (GI) toxicity, renal dysfunction and hepatic disease. Altered drug pharmacology in older patients may be a factor in their increased risk for drug toxicity. Elderly patients appear to be at greatest risk for symptomatic GI toxicity, including ulceration and even major GI bleeding. Central nervous system toxicity, characterized by dizziness, headaches, mood alteration and confusion, and renal dysfunction have also been reported to occur more commonly among elderly patients. Hepatic dysfunction is a rare NSAID-induced toxicity, but older patients are often at greatest risk for serious hepatic disease. Understanding the patient's underlying physiologic condition, concomitant drug therapy and the kinetics of the NSAID being used is critical to the safe administration of these agents to elderly individuals.

Lack of effect of piroxicam on theophylline clearance in healthy volunteers

This study was conducted to determine if piroxicam alters the clearance or metabolism of theophylline in healthy adults. Six male volunteers were given aminophylline 6 mg/kg iv before and after piroxicam treatment. Piroxicam 20 mg/d po was administered for seven days. Serum samples were collected before and for 24 hours after each aminophylline dose. Theophylline serum concentrations were determined using the Abbott TDx automated immunoassay system. Theophylline and its 1,3-dimethyluric acid metabolite were measured in 24-hour urine collections. Serum theophylline concentration versus time curves were plotted and pharmacokinetic parameters determined for each subject. None of the derived parameters differed as a result of piroxicam exposure. Theophylline metabolites, clearance, half-life, and volume of distribution were compared during the baseline and piroxicam phases and were found to be similar. It was concluded that piroxicam does not alter the clearance, distribution, volume, or metabolism of theophylline in healthy adult volunteers.

Effects of piroxicam on natriuresis and kaliuresis in hypertensives and healthy volunteers

The effects of short-term piroxicam (P) treatment on natriuresis and kaliuresis were evaluated in 22 diuretic-treated hypertensives and 8 healthy subjects. Each hypertensive patient participated in three experimental periods, i.e., P 20 mg q.d. for 3 days and two control phases. Each healthy volunteer completed the six treatment phases, i.e., P 20 mg q.d. for 3 days, furosemide 40 mg orally in a single dose, P 20 q.d. for 3 days with furosemide 40 mg on the third day and three control phases. In healthy volunteers, P induced no change in 24-hour natriuresis and kaliuresis, but it reduced furosemide-stimulated natriuresis. In hypertensives with creatinine clearance (CCr) greater than 60 ml/min, P had no anti-natriuretic and anti-kaliuretic effects. In contrast, P induced a significant reduction in 24-hour natriuresis and kaliuresis in those with CCr less than 60 ml/min. Physicians should be aware of the potential risk of P-induced sodium retention and hyperkalemia, especially in patients with renal insufficiency, even though P was administered for only 3 days.

Pharmacokinetics of aspirin in aged Indians

The pharmacokinetics of aspirin (ASA) has been studied in elderly Indians (greater than 60 y) of either sex, composing, apparently healthy subjects controlled hypertensives and NIDDM diabetics, in comparison with healthy young subjects. Serum salicylate levels were estimated a 0, 0.5, 1, 2, 4 & 8 h after ASA. The pharmacokinetics of serum salicylate were not changed in elderly subjects as compared to the young after the first dose or after one week of ASA therapy, although greater variability was observed in the elderly. Various laboratory investigations were unaltered after one week in all the groups, except that one elderly hypertensive patient gained weight, and a young subject showed an increase in SGOT & SGPT.

Lack of interaction between sulindac or naproxen and propranolol in hypertensive patients

Seventeen patients with hypertension and osteoarthritis participated in a single-blind crossover study comparing the effects of sulindac 200 mg twice daily, naproxen 500 mg twice daily, and placebo on blood pressure. All patients were treated for hypertension with propranolol monotherapy. Blood pressures were back-titrated to achieve a baseline diastolic blood pressure of 90 to 100 mm Hg while taking naproxen. There were no significant differences in mean sitting or standing blood pressures among the patients receiving naproxen, sulindac, or placebo treatments. There was no change in pulse, weight, or any of the laboratory measurements at the end of each treatment phase. These results suggest that neither sulindac nor naproxen interferes with propranolol therapy for uncomplicated hypertension.

Clinical aspects of renal prostaglandins and NSAID therapy

Nonsteroidal antiinflammatory drugs (NSAIDs) can have a variety of effects on renal function. Excluding allergic phenomena, these are directly related to NSAID-induced inhibition of renal synthesis of prostaglandins (PGs). For the most part, renal PGs play important physiological roles only in certain pathologic conditions. Thus, patients without these diseases (such as cardiac, hepatic, or renal compromise) manifest no or only trivial effects on renal function when NSAIDs are administered. This feature is to the advantage of the clinician because it allows prospective identification of patients who are at risk for an adverse renal effect; hence, such effects can be minimized or avoided altogether. To do so requires an understanding of the various roles of PGs in the kidney and thereby the effects that one can observe from NSAIDs. This review focuses on these various roles of renal PGs and on identification of patient groups at risk for adverse renal effects of NSAIDs.

A multicenter study of the safety and efficacy of naproxen: analysis of blood pressure

A multicenter study was conducted to determine safety and efficacy of naproxen, 500 mg twice daily, administered for 4 weeks to osteoarthritis (OA) patients. OA symptoms improved in the study population. The study population included 97 patients, 43 of whom were 65 years of age or older. Forty-four of the 97 patients had a history of hypertension; 42 of these took antihypertensive medication before and during the study. Baseline blood pressure (BP) was measured in most patients while they were receiving their prior nonsteroidal antiinflammatory drug (NSAID) therapy; from that baseline, no increase in BP was seen in the hypertensive or normotensive patients after 4 weeks of naproxen therapy. In patients whose BP was controlled by antihypertensive agents, BP remained under control during naproxen therapy.

Nonsteroidal antiinflammatory drug-induced renal dysfunction related to inhibition of renal prostaglandins

This article reviews the role of prostaglandins (PG) in maintaining renal function in the face of vasoconstrictive substances and decreased renal blood flow. Inhibition of the synthesis of renal PG by nonsteroidal antiinflammatory drugs (NSAID) may lead to the development of hemodynamically induced renal dysfunction in patients with a decreased effective plasma volume or chronic renal insufficiency. The importance of stimulation of renal PG activity to the action of diuretics and a pharmacodynamic mechanism for NSAID-induced diuretic resistance are presented. Evidence for the relative selectivity of sulindac in inhibiting systemic PG without inhibiting renal PG is also reviewed. Inhibition of renal PG synthesis has been postulated to be a contributing factor for other forms of NSAID-induced renal dysfunction (interstitial nephritis, analgesic-associated nephropathy). The relationship between renal PG inhibition by NSAID and these syndromes is briefly discussed. Considering the frequent use of NSAID, it is important that practitioners are aware of the mechanisms whereby patients may develop NSAID-induced renal dysfunction and that they are able to identify patients at risk.

Renal eicosanoids as determinants of renal function in liver disease

The available data suggest that alterations in renal prostaglandin metabolism participate in the pathogenesis of at least two prominent renal complications of liver disease: (a) sodium retention and (b) HRS. Although the data are highly suggestive, additional studies, including experimental manipulations that augment vasodilatory prostaglandins while diminishing vasoconstrictor metabolites of arachidonic acid, will be required to establish the role of prostaglandins or other arachidonic acid metabolites in mediating these renal abnormalities. The clinical caveat emerging from these observations is that every attempt should be made to avoid prescribing drugs which possess cyclooxygenase inhibitory activity to patients with decompensated liver disease who are sodium-avid.

The effects of naproxen and sulindac on renal function and their interaction with hydrochlorothiazide and piretanide in man

We have studied the effect of a single dose challenge of naproxen (500 mg) and sulindac (200 mg) on renal function in five volunteers, and the effect of a single dose challenge of the thiazide, hydrochlorothiazide (100 mg), and loop diuretic, piretanide (6 mg) on renal function when the diuretics were given alone or when superimposed on chronic therapy of either naproxen or sulindac. None of the nonsteroidal anti-inflammatory drug (NSAID) or diuretic exposures significantly influenced glomerular filtration rate, as measured by creatinine clearance. Over the first 4 h of the study, both naproxen and sulindac reduced fractional excretion of sodium by approximately 50%. Sulindac also caused a significant uricosuria whilst naproxen promoted urate retention. Similar changes were observed over 8 h. Superimposition of either hydrochlorothiazide or piretanide on top of chronic sulindac therapy resulted in a blunting of the natriuresis by approximately 30% compared to when these diuretics were given alone: the action of the diuretics was unchanged by naproxen. Sulindac pretreatment did not alter the urinary excretion of either hydrochlorothiazide or piretanide; naproxen did not alter hydrochlorothiazide excretion. On the basis of these findings, it is concluded that NSAIDs exert direct tubular effects that do not necessarily interfere with the delivery of diuretics to their sites of action within the nephron.

Role of renal prostaglandins and the effects of nonsteroidal anti-inflammatory drugs in patients with liver disease

Renal prostaglandins have several key functions in patients with severe liver disease and ascites. Increased activity of vasodilatory prostaglandins counters the underlying impairment in renal perfusion and the effects of vasoactive hormones. Prostaglandins also participate in renin secretion, renal diluting ability, sodium excretion, the action of diuretics, and, possibly, the development of the hepatorenal syndrome. Nonsteroidal anti-inflammatory drugs inhibit these compensatory actions of prostaglandins and cause a functional reduction in glomerular filtration rate and an impairment in sodium and fluid excretion. The severity of these nephrotoxic effects depends on the potency of the drug in inhibiting renal prostaglandins and on patient susceptibility. Patients with ascites and avid sodium retention, sodium-restricted diets, or concurrent diuretic use are most at risk. If nonsteroidal anti-inflammatory drugs must be administered to these patients, the type of drug should be carefully selected and renal function should be closely monitored.