A double-blind multicentre study of piretanide and hydrochlorothiazide in patients with essential hypertension

In a randomized double-blind parallel group study conducted in three centres the hypotensive activity of piretanide 6 mg b.i.d. was compared with that of hydrochlorothiazide (HCT) 25 mg b.i.d. and HCT 50 mg b.i.d. Ninety-three patients entered the study and sixty-one completed a 16-week trial period. All three treatments produced a significant reduction in supine diastolic and systolic blood pressure after only 2 weeks of active treatment and this was maintained for the duration of the study. The mean maximal reduction in supine diastolic blood pressure was 18% in the piretanide group, 18.8% in the HCT 25 mg b.i.d. group, and 20% in the HCT 50 mg b.i.d. group. The corresponding figures for the percentage of patients attaining a supine diastolic pressure below 95 mm Hg were 83%, 62% and 89%. There were no significant differences between the three groups. Side-effects were generally mild and transient, except for polyuria which was noted in all three groups but more commonly in the piretanide group. Two patients were withdrawn because of side-effects: one patient in the high dose HCT group developed severe postural symptoms; and one patient in the low dose HCT group was withdrawn because of restlessness, nausea, weakness, dizziness and somnolence. All three treatments caused a significant increase in serum uric acid concentrations. Four patients in each of the HCT groups developed hypokalaemia, but no patients in the piretanide group did so.

Vasopressin administration to neonatal rats reduces antidiuretic response in adult kidneys

Neonatal rats who had been given injections of vasopressin on days 1-7 after birth exhibited polyuria as adults. In vivo antidiuresis bioassays demonstrated that their kidneys were deficient in their ability to concentrate urine in response to stimulation with vasopressin. The kidneys also showed a reduction in vasopressin-induced cyclic AMP production, although parathyroid hormone- and calcitonin-induced levels were normal. This suggests a specific deficit in vasopressin receptor-adenylate cyclase function. In contrast, the neonatal treatment had no effect on the sensitivity of the adult vasculature to the hypertensive effects of vasopressin. These results show that short exposures to high levels of vasopressin early in development can produce a long-term defect in vasopressin responsiveness that is specific to the kidney.

Cortical and papillary absorptive defects in gentamicin nephrotoxicity

Renal function was examined in rats given daily injections of gentamicin (100 to 150 mg/kg) for 10 to 14 days. Whole kidney inulin clearance fell and urine volume increased. Single nephron GFR of surface nephrons varied. Some nephrons had no filtration, some had low rates, and some had high rates. Abnormal renal tubular epithelial inulin permeability was demonstrated by microinjection. Micropuncture of individual nephrons early and later in their course demonstrated reduced fluid reabsorption along the proximal convoluted tubule of superficial nephrons. Rates of fluid delivery to the late proximal and distal tubule were elevated. The rate of fluid reabsorption in the superficial loop of Henle was increased. Maximal urine osmolality and papillary tissue content of urea was reduced. The polyuria, therefore, results from decreased fluid reabsorption by proximal tubules and, probably, by papillary collecting ducts. The decrease in proximal fluid reabsorption is probably secondary to impaired solute reabsorption. A decrease in collecting duct fluid absorption can be attributed to the observed decrease in papillary solute concentration.

Acute polyuric renal failure after aspirin intoxication

Reversible acute polyuric renal failure was observed in a patient after the ingestion of an unusually large toxic (125 g) dose of aspirin. Renal dysfunction occurred in the absence of volume depletion or underlying renal impairment. These observations emphasize the need for careful monitoring of renal function in all patients with aspirin intoxication.

The renal concentrating defect after gentamicin administration in the rat

The present studies were carried out to delineate the mechanism of the polyuric state and renal concentration defect seen after gentamicin. Gentamicin was given at a dosage of 100 mg/kg/day subcutaneously for either 4 or 5 days to Sprague-Dawley rats and resulted in a reversible, polyuric form of acute renal failure. This nonoliguric acute renal failure was accompanied by significant polydipsia and a renal concentrating defect 11 days after gentamicin. To assess the role of polydipsia in the polyuria and renal concentrating abnormality, water intake was restricted in gentamicin-treated animals to match intake of control animals. Elimination of the polydipsia failed to eliminate the polyuria and to improve the renal concentrating abnormality. Postdehydration plasma vasopressin levels were higher in gentamicin-treated than control animals, suggesting that the renal concentrating defect was nephrogenic in origin. Daily urinary prostaglandin E2 excretion was comparable in gentamicin-treated and control animals. However, indomethacin failed to improve urinary concentrating ability, suggesting that the renal concentrating defect was prostaglandin E2 independent. Finally, depressed postdehydration inner medullary tonicity was found in gentamicin-treated animals In summary, gentamicin administration in the rat was associated with a reversible polyuric form of acute renal failure and a renal concentrating defect. This concentration defect was nephrogenic in origin, independent of polydipsia and prostaglandin E2, and was associated with a decrease in inner medullary tonicity.

The influence of age on lithium efficacy and side-effects in out-patients

One hundred and sixty-six unipolar and bipolar out-patients (21-78 years) on long-term lithium treatment were studied on a prospective basis. Although there was a possible tendency for manic attacks to increase in prevalence and severity with age, it was difficult to demonstrate a general age-related decline in lithium efficacy. There was a tendency for the prevalence and severity of fine hand tremor to increase with age. This was not seen with polydipsia/polyuria, the other typical lithium side-effect.

The responses to water deprivation in lithium-treated patients with and without polyuria

1. Urine osmolality and plasma and urine arginine vasopressin (AVP) were measured before, during and at the end of 23 h of water deprivation in four groups of subjects. There were eight non-polyuric manic-depressive patients taking lithium (the lithium group), seven manic-depressive patients taking other psychotropic drugs but not lithium (the other drug group), seven healthy subjects (the control group) and three lithium-treated patients with polyuria (the polyuric lithium group).

2. The lithium group had a resistance to the effect of AVP on the renal tubule with a fivefold increase in AVP excretion at a given urine osmolality. However, their water homoeostasis was intact as they lost no more weight during water deprivation than did the control group.

3. The relationship beween urine osmolality and AVP excretion has been defined from these results and the effect of lithium treatment on it has been characterized. The results suggest that lithium competitively inhibits the effect of AVP on the renal concentrating mechanism but does not decrease the ‘theoretical’ maximum urine osmolality.

4. The other drug group had a high basal urine flow which was due to a primary increase in water intake. The responsiveness of the renal concentrating mechanism to AVP was the same in this group as in the control group.

5. The polyuric lithium group had the highest basal urine flow and lost the greatest amount of weight during water deprivation. Neither urine osmolality nor AVP excretion was at a maximum in the basal state, as both increased during water deprivation. These relationships between urine osmolality and AVP excretion indicated a much greater resistance to AVP than in the other lithium-treated patients.

6. We suggest that these patients are polyuric as they become thirsty and drink before their AVP secretion increases to levels high enough to overcome the resistance to AVP. The results suggest, however, that in the basal state their water intake may be more than the minimum determined by the resistance to AVP.

Early polyuria in the rat following single-dose cis-dichlorodiammineplatinum (II): effects on plasma vasopressin concentration and posterior pituitary function

Central effects associated with DDP-induced early polyuria are described. Male Sprague-Dawley rats injected intraperitoneally with DDP (5 mg/kg) have a threefold increase in urine volume in the first 24 hr after treatment. This is accompanied by a corresponding decrease in Uosm but no decrease in renal function as indicated by serum creatinine or GFR. Treated animals having free access to water have reduced levels of plasma AVP, 1.42 +/- 0.14 pg/ml compared to 2.63 +/- 0.47 for control, at 8 hr after injection, and treated animals deprived of water have decreased plasma AVP at 12 and 24 hr after injection. The early polyuria in DDP-treated animals can be prevented by the administration of exogenous AVP. At 8 hr after DDP injection, posterior pituitary AVP content is identical in treated and control rats. In vitro studies with isolated pituitaries show that DDP, either 0.85 and 1.7 mM, in the medium inhibits AVP release by 60% to 90% during two successive 10 min incubation periods. These results suggest that DDP inhibits AVP release from the posterior pituitary but has no effect on AVP synthesis. This inhibition of AVP release results in lowered plasma AVP levels, which reduces water reabsorption and causes polyuria.

A longitudinal survey of side effects in a lithium clinic

The cross-sectional and longitudinal patterns of lithium side effects were surveyed in a prospective 12-month study. The use of other psychotropic medication (antidepressants, neuroleptics) in addition to lithium was associated with a higher frequency of complaints. The presence of noneuthymic mood was not associated with changes in the incidence of side effects. Persistent side effects were not related to current age, age at onset of illness, severity of illness, or duration of lithium therapy. The chronicity of lithium therapy was not specifically associated with the presence or absence of any of the 23 side effects surveyed.

Lithium's effects on the kidney

Although lithium was known to cause changes in renal physiology, it was considered safe until reports in late 1977 suggested that it may induce chronic irreversible nephropathy. Later reports documented similar lesions in non-lithium-treated patients with affective disturbances. Thus, the data are inconclusive. Concern for the kidney during lithium therapy is now greater than it was originally, but confidence in lithium's safety is higher than it has been for the past four years. Physician appreciation of the foregoing factors, careful patient selection, and informed consent are important in lithium therapy. An understanding of lithium use in patients in a low-sodium state or on diuretic therapy and avoidance and treatment of lithium intoxication are advocated. Good prelithium workups and closer monitoring of patients on long-term lithium therapy are recommended.

The role of prostaglandins in diabetes insipidus produced by desoxycorticosterone in the dog

To determine the role of renal prostaglandins (PGs) in the renal response to desoxycorticosterone acetate (DOCA), dogs were studied on a constant diet in which sodium intake was restricted (2.5 meq/day) or high (115 meq/day). On the restricted sodium intake, DOCA (25 mg/day im for 6 days) did not affect urinary volume, sodium, potassium, PGE2, or PGF2 alpha. On the high sodium intake, DOCA produced sodium retention for 1 day and a sustained increase in urinary potassium with a fall in serum potassium to 3.1 meq/liter. Urine volume increased from 574 +/- 50 to 1726 +/- 177 ml/day (P less than 0.001) with a fall in urinary osmolality from 1545 +/- 122 to 495 +/- 55 mosmol/ liter (P less than 0.001) as serum sodium increased from 149.0 +/- 1.0 to 152.5 +/- 0.3 meq/liter (P less than 0.025) by the sixth day of DOCA. Urinary PGE2 and PGF2 alpha were unchanged during the first 2 days of DOCA, then increased progressively from control values of 261 +/- 60 and 1143 +/- 144 ng/day ng/day, respectively, to 730 +/- 62 (P less than 0.005) and 3013 +/- 479 ng/day (P less than 0.01), respectively. Potassium repletion during continued DOCA treatment restored urinary volume, osmolality, PGE2 and PGF2 alpha, and serum sodium to control values. Treatment with indomethacin during DOCA-induced hypokalemia, polyuria, hypernatremia, and increased urinary PG, restored urinary PGs to control values, and corrected the polyuria and hypernatremia without a change in serum potassium. Thus, DOCA produced potassium depletion, polyuria, increased urinary PGs, and hypernatremia in dogs on a high sodium intake but not in those on a restricted sodium intake. As polyuria and hypernatremia were corrected either by potassium repletion, which corrected the supranormal renal synthesis of PGs, or by indomethacin, which inhibited their synthesis, renal water loss was presumably the result of an increase in renal PG synthesis, probably stimulated by potassium depletion.

Lithium prophylaxis and the kidney

We reviewed the records of 44 patients under age 55 with bipolar affective disorder, who were without known systemic illness and receiving lithium prophylactically for a minimum of 6 months. We systematically collected all demographic, family history, and clinical side-effect data. In addition, laboratory results of renal function were compiled. Polyuria was the earliest and most frequent side effect of lithium therapy. Patients receiving other psychotropic medication, plus lithium, showed a significant increased prevalence of polyuria particularly after 3 months of exposure to medication, as compared to patients receiving lithium alone. The onset of polyuria was correlated with duration of lithium treatment and patient's age at initiation of therapy. Our data suggest that polypharmacy, duration of exposure to lithium ion and patient age each predict the development of delayed polyuria, a symptom consistent with interstitial nephritis.

Some hazards of lithium use

The increasingly widespread use of lithium has benefited many, but the therapeutic potential of the drug will not be realized if it is used in a way that is haphazard or inattentive or adheres too rigidly to written guidelines. The authors present clinical vignettes that are representative rather than comprehensive examples of misadventures which can occur during the course of lithium therapy. They hope to stimulate a more knowledgeable, flexible, open-minded, and individualized approach to the use of this drug.

Effects of lithium on rat tail nerve conduction velocity

Orthodromic and antidromic conduction velocities were measured in the tail nerve of rats given lithium throughout life. Lithium at nontoxic levels failed to influence nerve conduction velocities. Lithium at toxic levels (2 X 2.5 mmol/kg/day for 7 days) produced overt signs of lithium intoxication and reduced both orthodromic and antidromic nerve conduction velocities. The reductions in conduction velocities were related inversely to the level of lithium in serum and red blood cells. Conduction velocities returned to normal levels after cessation of the toxic lithium treatment. The findings show life-long administration of lithium at nontoxic levels to be without adverse effects on peripheral nerves in rats, while toxic lithium levels caused reversible impairment in conduction properties in peripheral nerves.

5-Azacytidine and renal tubular dysfunction

During initial trials of 5-azacytidine in adults with advanced acute leukemia, we unexpectedly observed acid-base, fluid, and electrolyte abnormalities that contributed directly to the deaths of two early patients. To evaluate this toxicity further, we studied 22 patients who received a total of 33 courses of combination chemotherapy that included 5-azacytidine. During 29 courses (88%) of treatment, polyuria, glucosuria, and/or transient changes in the serum concentrations of bicarbonate or phosphorus were detected. Spontaneous polyuria with demonstrable salt wasting and orthostatic hypotension occurred during seven courses (21%) of treatment. Inappropriate glucosuria was observed in nine courses (27%). In 24 courses (73%) the serum bicarbonate fell below the normal range. The urine became alkaline during 12 of these instances; the anion gap was not increased during the acidosis. Hypophosphatemia with serum phosphorus concentrations as low as 0.3 mg/dl occurred in 21 of 32 evaluable courses (66%). In the three patients studied the tubular reabsorption of phosphorus was 10%-18%. The renal abnormalities that were observed suggest both proximal and distal tubular damage from 5-azacytidine. Patients receiving 5-azacytidine should be monitored closely for manifestations of renal toxicity.

Attenuation of the lithium-induced diabetes-insipidus-like syndrome by amiloride in rats

The effect of amiloride on lithium-induced polydipsia and polyuria and on the lithium concentration in the plasma, brain, kidney, thyroid and red blood cells was investigated in rats, chronically treated with LiCl. Amiloride reduced the drinking and urine volume of rats in an acute (6 or 12 h) and a subacute (3 days) experiment. 6 h after the administration of amiloride, a reduction was observed in the lithium content of the renal medulla but not in the other organs studied. At 12 h, all the tissues showed a slight increase in lithium levels. After 3 days of combined treatment, a marked elevation in plasma and tissue lithium levels accompanied a reduction in water intake. In all the experiments, the attenuation of the lithium-induced diabetes-insipidus-like syndrome by amiloride was accompanied by a reduction of the ratio between the lithium concentration in the renal medulla and its levels in the blood and an elevation in the plasma potassium level. It is concluded that acute amiloride administration to lithium-treated patients suffering from polydipsia and polyuria might relieve these patients but prolonged amiloride supplementation would result in elevated lithium levels and might be hazardous.

Glomerular filtration rate and calcium metabolism in long-term lithium treatment

Does long-term lithium treatment induce an irreversible renal damage, and does polyuria or changes in the calcium metabolism indicate this? To elucidate these questions GFR, diuresis, S-Ca, S-Mg, S-PTH and bone mineral content (photonabsorptiometry) were determined in 29 consecutive patients on long-term lithium therapy for 2.5--12 years and in 4 patients, who had been admitted to the Renal Clinic with lithium-induced polyuria. Only 1 of the patients had had a known lithium intoxication (S-Li > 2 mmol/l). None had a history of renal disease or significant analgesic consumption. In the consecutive series the GFR was not significantly reduced and no correlations were found between this parameter and the duration of lithium therapy, average S-Li, highest S-Li noted, diuresis or any of the calcium parameters. The morning diuresis was significantly increased in comparison with a control group with normal kidney function. 2 of the 4 polyuric patients had a decreased GFR, but in 1 case it was normalized on desmopressin supplementation. Renal biopsy in the patient with one S-Li of 2.35 and a low GFR in the consecutive series, and in 3 of the polyuric patients, revealed focal interstitial fibrosis and nephron atrophy. The mean S-Ca, S-Mg, S-PTH and bone mineral content were increased, but no significant intercorrelations between these parameters were found. Neither were any intercorrelations found between the calcium parameters and time on lithium therapy, average S-Li, highest S-Li noted or morning diuresis. In conclusion a relatively well-managed lithium therapy for up to 12.5 years does not seem to influence the GFR, even if renal biopsy in 4 of our patients revealed interstitial nephritis and data in the literature indicate a progressive interstitial nephritis. The present study did not support the proposition that polyuria is an alarming sign of pronounced renal lesion. Calcium metabolism is influenced by lithium therapy but from the clinical point of view no negative effects could be found. S-Ca should probably be checked regularly in patients on long-term lithium therapy.

Lithium-induced polyuria: effect of lithium on adenylate cyclase and adenosine 3',5'-monophosphate phosphodiesterase in medullary ascending limb of Henle's loop and in medullary collecting tubules

We investigated the effects of hyperosmolality, chronic treatment with lithium chloride (LiCl), and the addition of LiCl in vitro on vasopressin-sensitive (VP) adenylate cyclase (AdC) and cAMP phosphodiesterase (cAMP-PDIE) activities in the medullary thick ascending limb of Henle's loop (MAL) and medullary collecting tubule (MCT) microdissected from the outer medulla of the rat kidney. A hyperosmolar medium (800 mosmol) markedly enhanced AdC activity stimulated by 10(-6) M VP specifically in MCT, while having little effect or slightly decreasing VP-stimulated AdC in MAL, compared to activities under standard isotonic conditions. Hyperosmolality decreased cAMP-PDIE activity to about the same degree in MAL and MCT. Inclusion of LiCl in the incubation medium (15-20 mM) caused a significant dose-dependent inhibition of VP-stimulated AdC activity in both MAL and MCT, but had no effect on CAMP-PDIE in either segment. AdC and cAMP-PDIE activities in MAL and MCT from chronic LiCl-treated polyuric rats did not differ from controls when assayed under standard isotonic conditions. However, when assayed in a hyperosmolar (800 mosmol) medium, VP-sensitive AdC activity was significantly lower (P < 0.01) in MCT from LiCl-treated rats compared to control levels, while VP-sensitive AdC in MAL did not differ in LiCl-treated and control rats. The present results suggest that lowered VP-sensitive AdC activity in MCT of LiCl-treated polyuric rats may contribute to the observed lower concentrating ability and collecting tubule resistance to VP. Inhibition of VP-sensitive AdC in MAL as well as MCT by the acute addition of LiCl in vitro may explain the decreased urinary diluting ability observed with acute infusions of Li salts in vivo in the rat.