Mechanism of attenuated hydrochlorothiazide response during indomethacin administration

Transplantation of a Gitelman Syndrome Kidney Ameliorates Hypertension: A Case Report

Gitelman syndrome is caused by inactivating mutations of the gene that encodes the renal sodium/chloride cotransporter (NCC; encoded by SLC12A3), resulting in hypokalemia, hypomagnesemia, hypocalciuria, and metabolic alkalosis. Renal salt wasting commonly provokes mild hypotension. The paucity of previous kidney transplants from donors with known tubulopathies suggests that such conditions may be considered contraindications to donation. A 76-year-old man received a live unrelated kidney transplant from a donor with known Gitelman syndrome secondary to a pathogenic mutation of SLC12A3. Immediate graft function preceded the emergence of the Gitelman syndrome biochemical phenotype and blood pressure subsequently improved. The recipient developed unexpected hyponatremia. Potential causes are discussed, including the possibility that it paralleled the physiologic changes seen in the high-volume state of thiazide-induced hyponatremia. Transplanted kidneys are subject to nephrotoxicity from the use of calcineurin inhibitors. Acquired Gitelman syndrome may confer a potential long-term advantage to the recipient through both improved blood pressure control and protection against the calcineurin inhibitor-induced side-effect profile caused by NCC overactivation. Both the donor and recipient remain well. In conclusion, Gitelman syndrome need not preclude kidney donation and transference of the phenotype may have benefits for the recipient.

Indomethacin, amiloride, or eplerenone for treating hypokalemia in Gitelman syndrome

Patients with Gitelman syndrome (GS), an inherited salt-losing tubulopathy, are usually treated with potassium-sparing diuretics or nonsteroidal anti-inflammatory drugs and oral potassium and magnesium supplementations. However, evidence supporting these treatment options is limited to case series studies. We designed an open-label, randomized, crossover study with blind end point evaluation to compare the efficacy and safety of 6-week treatments with one time daily 75 mg slow-release indomethacin, 150 mg eplerenone, or 20 mg amiloride added to constant potassium and magnesium supplementation in 30 patients with GS (individual participation: 48 weeks). Baseline plasma potassium concentration was 2.8±0.4 mmol/L and increased by 0.38 mmol/L (95% confidence interval [95% CI], 0.23 to 0.53; P<0.001) with indomethacin, 0.15 mmol/L (95% CI, 0.02 to 0.29; P=0.03) with eplerenone, and 0.19 mmol/L (95% CI, 0.05 to 0.33; P<0.01) with amiloride. Fifteen patients became normokalemic: six with indomethacin, three with eplerenone, and six with amiloride. Indomethacin significantly reduced eGFR and plasma renin concentration. Eplerenone and amiloride each increased plasma aldosterone by 3-fold and renin concentration slightly but did not significantly change eGFR. BP did not significantly change. Eight patients discontinued treatment early because of gastrointestinal intolerance to indomethacin (six patients) and hypotension with eplerenone (two patients). In conclusion, each drug increases plasma potassium concentration in patients with GS. Indomethacin was the most effective but can cause gastrointestinal intolerance and decreased eGFR. Amiloride and eplerenone have similar but lower efficacies and increase sodium depletion. The benefit/risk ratio of each drug should be carefully evaluated for each patient.

Antihypertensive drugs and endothelial cell function

Arterial hypertension is associated with increased capillary permeability, a possible contributor to the vascular remodeling process which could be involved in certain pathological conditions arising from elevated blood pressure. This study evaluated the effects of various antihypertensive drugs on capillary permeability in the normal rat, using Evan's blue dye (EB) as a marker of albumin extravasation. The results reveal that acute injection of certain diuretics (furosemide, indapamide, hydrochlorothiazide) increase while others (amiloride, cicletanine) decrease capillary permeability via stimulation of the cyclooxygenase pathway. 10 day gavage with indapamide, amiloride and cicletanine, as well as angiotensin-converting enzyme (ACE) inhibitor perindopril and calcium channel blockers nifedipine and verapamil decreases capillary permeability, whereas furosemide, hydrochlorothiazide, ACE inhibitor captopril and calcium channel blocker clentiazem do not modify or increase EB extravasation. Hence, selected antihypertensive agents reduce capillary permeability and could therefore have a supplemental protective vascular effect, in addition to their lowering arterial pressure.

Prostaglandin synthesis inhibition stimulates lithium reabsorption in Henle's loop in rats

The effect of prostaglandin (PG) synthesis inhibition on tubular lithium (Li) handling in the rat was studied by micropuncture at the late proximal (LPT) and early distal (EDT) tubules. Animals received no treatment (N = 7), meclofenamate (MECLO; 5 mg/kg i.p. and 5 mg/kg i.v.; N = 7) or indomethacin (INDO, 1 mg/kg i.v.; N = 6). Whole kidney fractional Li excretion fell from 26.2 +/- 1.5% in control rats to 12.8 +/- 1.3% and 14.6 +/- 1.3% in MECLO and INDO treated rats. Fractional delivery of Li to the LPT was not affected by PG synthesis inhibition. All of the rise in tubular Li reabsorption took place between the LPT and EDT; at the EDT fractional Li delivery fell from 32.3 +/- 2.0% in the control group to 19.1 +/- 1.6% and 20.0 +/- 1.4% in the rats given MECLO or INDO. Water reabsorption between the LPT and EDT also increased. The tubular fluid/plasma Li concentration ratio ([T/P]Li) at the LPT was approximately 1.15 in all groups of rats. At the EDT, this ratio was approximately 1.06 in control rats, but only approximately 0.82 (P < 0.01) in rats subjected to PG synthesis inhibition. The finding that the [T/P]Li fell from values exceeding unity at the LPT to values below unity at the EDT during PG synthesis inhibition indicates that reabsorption of Li between these sites was stimulated to a greater extent than that of water. This dissociation strongly suggests that at least part of the increased Li reabsorption between the LPT and EDT took place in the water-impermeable thick ascending limb.(ABSTRACT TRUNCATED AT 250 WORDS)

The problems of using NSAIDs in the elderly

It has been estimated that, in the United Kingdom, at least, women over the age of 65 years are more likely than not to have taken a nonsteroidal anti-inflammatory drug (NSAID). It is against this enormous use that reports of toxicity must be balanced. There has been a tendency during the past decade to deprecate the use of NSAIDs, especially in the elderly. Yet, despite the well-known problems associated with these agents in older patients, such as reduced glomerular filtration rate, this group of drugs is tolerated surprisingly well. Nevertheless, some NSAIDs do have a greater propensity to cause gastrointestinal bleeding, especially in older female patients. Ketoprofen, metabolized by the liver, may have advantages over other NSAIDs in the elderly. This paper reviews the problems associated with the use of NSAIDs in older patients. In general, NSAIDs have proved to be an advance in the management of rheumatic diseases in the elderly, displacing the far more toxic aspirin.

Influence of indomethacin on extracellular calcium homeostasis

Rheumatoid arthritis is associated with a generalised loss of bone mass. One of the factors that have been implicated in the pathogenesis of this bone loss is the chronic use of non-steroidal anti-inflammatory drugs (NSAIDs). These drugs are known to increase gastrointestinal permeability and may thus influence the absorption of calcium; they may also influence glomerular filtration rate and the renal excretion of calcium; in addition, NSAIDs may inhibit osteoblast function as well as osteoclastic bone resorption. Calcium homeostasis was studied in eight healthy volunteers during eight days' treatment with 150 mg indomethacin daily. No changes in serum concentration of calcium, phosphorus, parathyroid hormone, 25-hydroxyvitamin D3, and 1,25-dihydroxyvitamin D3 were found. The creatinine clearance and the urinary excretion of phosphorus and sodium did not change, but a decrease in calcium excretion was noted (mean (SEM) calcium/creatinine excretion 0.52 (0.05) v 0.28 (0.06)). This decrease is probably due to renal retention of calcium. Whether this decrease of urinary calcium excretion has a positive or a negative effect on bone is presently unknown.

Evaluation of lithium clearance as a marker of proximal tubule sodium handling

Estimations of proximal tubule sodium reabsorption with the FELi method come closer to direct measurements than any other indirect method. There is little doubt that most lithium reabsorption takes place in the proximal tubules, very likely in proportion to the reabsorption of sodium and water. It is also likely that changes in proximal tubule sodium reabsorption due to changes in volume status are paralleled by changes in proximal tubule lithium reabsorption, at least in the superficial nephrons. Nonetheless, changes in FELi probably do not purely reflect changes in proximal reabsorption, since lithium is also handled beyond the proximal tubules. Acknowledged problems are lithium reabsorption in Henle's loop and in the late distal and collecting tubules. The latter occurs in the rat and the dog, but not or much less in men. Sodium restriction enhances this lithium transport considerably. It is as yet uncertain whether other conditions, such as increased vasopressin activity or lowering of renal perfusion pressure, also influence this transport. Amiloride appears to prevent this reabsorption of lithium. Therefore, this drug can be used in lithium clearance studies whenever unwanted "distal" lithium reabsorption is expected. Lithium reabsorption in Henle's loop forms a greater problem as it cannot be prevented by any drug without influencing proximal tubule reabsorption. It is estimated that about 7% of the filtered lithium (one-tenth of total lithium reabsorption) is normally taken up here, preferentially in deep nephrons. In view of studies with furosemide, this reabsorption probably varies with sodium intake, but the proportion of this variation to that of proximal tubule lithium reabsorption is obscure. This remains an uncertain factor in any circumstance where the lithium clearance method is used. In some conditions the change in FELi may be so large relative to the expected changes in proximal reabsorption, that use of FELi as marker of end-proximal solute delivery seems unjustified. Disproportionately large suppression is likely during mineralo-corticoid-induced volume expansion, and stimulation during prostaglandin synthesis inhibition and vasopressin. Based on observations in these conditions the potential range of lithium reabsorption in the loop of Henle would be 0 to 15% of filtered load. In this review attention was paid mainly to the validity of lithium clearance as a pure "proximal marker". Many of our interpretations suffer from incomplete certainty with respect to the renal effects of tested maneuvers, a problem which is acknowledged.(ABSTRACT TRUNCATED AT 400 WORDS)

Drug interactions with non steroidal anti-inflammatory drugs (NSAIDs)

Drug interactions occur when the pharmacologic profile of one drug is altered by the administration of another drug. These interactions may be due to changes in absorption, distribution, metabolism or excretion. NSAIDs are associated with drug interactions but only a proportion are clinically relevant. Many are due to displacement of a drug from its plasma protein binding sites by NSAIDs which are tightly protein-bound. They may not occur with all NSAIDs but might be selective: most NSAIDs do not have clinically important interactions with oral hypoglycemic agents whereas phenylbutazone, azaprozone & aspirin prolong their half-life. Similarly phenylbutazone and azaprozone prolong coumadin's half-life. Lithium clearance may be decreased by indomethacin, piroxicam, phenylbutazone and diclofenac. Methotrexate (MTX) may be displaced from its binding protein sites by NSAIDs. This is generally not clinically relevant with low doses of MTX as utilized in rheumatoid arthritis patients with normal renal function. NSAIDs also may reduce renal blood flow, tubular excretion of drugs & renal prostaglandin production and may attenuate the effect of anti-hypertensive drugs. Renal failure & hyperkalemia have been reported in patients receiving triamterene & indomethacin. The clinician should be aware of important drug-drug interactions prior to prescribing NSAIDs. Continued scrutiny of these effects are indicated to increase the safety profile.

The basis for variability of response to anti-rheumatic drugs

The reasons for variability of response to anti-rheumatic drugs are myriad. All the factors that contribute to kinetic variability, for example, contribute to differences in response between individuals. Thus, differences in drug formulation, protein binding, drug metabolism and excretion, all contribute to variable responses. Further, factors which contribute to differential clinical response/toxicity must be considered. Here, age, gender, genetic background, weight, concomitant diseases and numerous environmental factors come into play. Among the environmental factors are such diverse elements as smoking, activity and diet. Finally our ability to measure change, be it in response or toxicity, is limited, introducing apparent variability (as much as real variability) into the equation. While we cannot, at present, delineate the contribution of each factor to individual variability, it is hoped that systematic, persistent effort will help us understand and then control these elements, leading to improved ability to individualize therapy and decrease the variability of response to anti-rheumatic drugs.