Potential low toxic alternative for Na-Cl cotransporter inhibition: A diuretic effect and mechanism study of Pyrrosia petiolosa.

BACKGROUND: Hydrochlorothiazide, a diuretic commonly used for the treatment of hypertension, is often associated with serious metabolic side effects. Pyrrosia petiolosa (Christ) Ching is a traditional Chinese medicine that possesses diuretic properties, without any obvious side effects. AIM: To evaluate the diuretic effect of P. petiolosa (Christ) Ching and to elucidate its underlying mechanism of action. METHODS: Extracts obtained from different polar components of P. petiolosa (Christ) Ching were analyzed for toxicity in a Kunming mouse model. The diuretic effects of the extracts were compared to that of hydrochlorothiazide in rats. In addition, compound isolation procedures, cell assays of Na-Cl cotransporter inhibition and rat diuretic test of monomeric compounds were conducted to identify the active ingredients in the extract. Subsequently, homology modeling and molecular docking were performed to explain the reason behind the diuretic activity observed. Finally, LC-MS analysis was used to elucidate the underlying mechanism of action of P. petiolosa (Christ) Ching. RESULTS: No toxicity was observed in mice administered P. petiolosa (Christ) Ching extracts. The ethyl acetate fraction showed the most significant diuretic effect. Similar results were obtained during the analysis for Na+ content in rat urine. Further separation of P. petiolosa (Christ) Ching components led to the isolation of methyl chlorogenate, 2',3'-dihydroxy propyl pentadecanoate, and ß-carotene. Results from cell assays showed that the Na-Cl cotransporter inhibitory activity of methyl chlorogenate was greater than that of hydrochlorothiazide. This result was again confirmed by the diuresis tests of monomeric compounds in rats. The molecular simulations explain the stronger interactions between the methyl chlorogenate and Na-Cl cotransporter. Of the compounds determined using LC-MS analysis, 185 were identified to be mostly organic acids. CONCLUSIONS: P. petiolosa possesses significant diuretic activities without any obvious toxicity, with least two possible mechanisms of action. Further study on this herb is warranted.

Enalapril protect human lymphocytes from genotoxicity of Hydrochlorothiazide.

Hydrochlorothiazide (HCTZ) belongs to the thiazide diuretics family that is used for the treatment of hypertension. Enalapril is another drug that is used for the treatment of hypertension. Recently, both drugs were combined in a single medication called vaseretic that showed a strong synergistic effect against hypertension. The aim of this investigation is to examine genotoxicity of HCTZ/enalapril on chromosomal damage by measuring the frequency of sister-chromatid exchanges (SCEs) in cultured human lymphocytes. Findings showed that HCTZ (5µg/mL) significantly increased SCEs frequency (P<0.01) in cultured cells relative to the untreated cells. The levels of SCEs induced by Enalapril (10µg/mL) was similar to the level detected in the untreated cultures (P>0.05). Interestingly, SCEs induced by combined treatment were significantly lower than HCTZ alone (P<0.05). Thus, enalapril seems to protect lymphocytes from genotoxicity induced by HCTZ. Neither HCTZ nor enalapril treatment (alone or in combination) induced changes in the mitotic index and the proliferative index (P>0.05). In conclusion, HCTZ increased SCEs in cultured lymphocytes, and this increase is reduced by enalapril.

An investigation of the mutagenic activity of salamide - a major impurity of hydrochlorothiazide.

Hydrochlorothiazide is a widely used antihypertensive agent and one of its major impurities, salamide (4-amino-6-chlorobenzene-1,3-disulphonamide), has a chemical structure containing a primary amino group, a functional group that has previously been reported to be associated with carcinogenic activity. It is known that hydrochlorothiazide purity is a challenging problem for the pharmaceutical industry. As there were no prior mutagenicity data for the impurity salamide, the aim was to investigate its mutagenicity in this study. Salamide was tested for mutagenic potential in Salmonella typhimurium TA98, TA100, TA 1535, TA 1537, and E. coli WP2 uvrA + E. coli WP2 [pKM101] strains at six different concentrations, the highest concentration being the 5000 µg/plate. In both the presence and absence of the metabolic activation system, no mutagenic activity was observed. Results indicated that salamide should be classified as an ordinary impurity and controlled according to Q3A(R2) and Q3B(R2) guidelines.

Characterization and evaluation of multi-component crystals of hydrochlorothiazide.

PURPOSE: The present work aims at improving the physicochemical properties of hydrochlorothiazide, a poorly water soluble antihypertensive drug by preparing its multi-component crystals with nicotinic acid (HCT-NA) and 2-picolinic acid (HCT-PIC). METHODS: The crystals prepared by solution crystallization were investigated by thermoanalytical techniques. The crystal structures of HCT-NA (1) and HCT-PIC (2) were determined by the single crystal X-ray diffraction and were assessed for their aqueous solubility, antihypertensive activity and acute toxicity in rats. RESULTS: Both 1 and 2 crystallized in the orthorhombic space group P212121 and formation of salts were confirmed. The solubility profiles of 1 and 2 in basic media showed a maximum release of 2.5 mg/ml and 1.9 mg/ml, respectively, in comparison to the drug (0.82 mg/ml). The in-vivo antihypertensive activity of 1 in deoxycorticosterone acetate salt induced hypertensive rats showed 1.5 fold improvement. No increase in the signs of toxicity were revealed in rats during the acute toxicity studies even at doses of 2,000 mg/kg by body weight in comparison to the free drug. Histopathological findings supported the safety of these multi-component crystals. CONCLUSIONS: The new solid phases exhibit potential to be explored for the oral drug delivery of HCT with improved solubility and therapeutic outcome.

Effect of combined treatment with diuretics and gabapentin on convulsive threshold in mice.

Research data show that diuretics can have anticonvulsant properties. This study examined effects of ethacrynic acid, a loop diuretic, and hydrochlorothiazide, a thiazide-type diuretic, on the anticonvulsant activity of gabapentin, a newer antiepileptic drug, in the maximal electroshock seizure threshold test in mice. Diuretics were administered intraperitoneally (ip.) both acutely (single dose) and chronically (once daily for seven days). Electroconvulsions were produced by an alternating current (50 Hz, 500 V, 0.2 s stimulus duration) delivered via ear-clip electrodes by a generator. Additionally, the influence of combined treatment with the diuretics and gabapentin on motor performance in the chimney test has been assessed. In the current study, ethacrynic acid at the chronic dose of 12.5 mg/kg and the single dose of 100 mg/kg did not affect the anticonvulsant activity of gabapentin. Similarly, hydrochlorothiazide (100 mg/kg), both in acute and chronic experiments, had no effect on the gabapentin action. On the other hand, in the chimney test, the combined treatment with ethacrynic acid (100 mg/kg) and gabapentin (50 mg/kg) significantly impaired motor performance in mice. Based on the current preclinical findings, it can be suggested that the diuretics should not affect the anticonvulsant action of gabapentin in epileptic patients. However, the combination of ethacrynic acid with gabapentin may cause neurotoxicity.

Retinal phototoxicity induced by hydrochlorothiazide after exposure to a UV tanning device.

UV radiation is known to cause acute and chronic eye and skin damage. The present case report describes the occurrence of hydrochlorothiazide-induced retinal phototoxicity immediately after exposure to UV light emanated from a sunbed in a 40-year-old myopic woman. During the tanning session she had always worn UV protective eyewear, except for a few minutes when she took the protective goggles off to put her spectacles on to locate and turn the timer switch off. At baseline her visual acuity was 10/25 in OD and 10/80 in OS. Fundus examination revealed the presence of retinal lesions in both eyes. More specific tests confirmed the presence of a phototoxic macular damage. Hydrochlorothiazide was discontinued, and she was recommended to wear UV filtering glasses. Over the follow-up period (12 months), a slow and progressive visual acuity recovery in both eyes occurred. At the last check the visual acuity improvement was of about 60% from baseline in both eyes. Fundus examination showed only a juxtafoveal flat pigmented scar of the retinal pigment epithelium in both eyes, milder in OD. The constant rise in the number of sunbed users makes the knowledge of UV-related side effects a problem that cannot be postponed further. Awareness of the general public about the harmful effects of UV exposure must represent one of the leading preventive health strategies. Therefore, a careful analysis of the medical history before the admission to a sunbed session throughout a questionnaire could represent an economic and effective measure to avoid further cases of a phototoxic macular damage in patients taking photosensitizing compounds.

Genotoxicity of hydrochlorothiazide in cultured human lymphocytes. I. Evaluation of chromosome delay and chromosome breakage.

Hypertension is often treated with diuretics, like hydrochlorothiazide (HCTZ). Previous results on the in vitro genotoxicity of HCTZ are equivocal. In the present study, we have evaluated the genotoxicity of HCTZ in cultured human lymphocytes using the Cytokinesis Blocked Micronucleus (CBMN) assay. In addition, micronucleus (MN) induction was analyzed by Fluorescence In Situ Hybridization (FISH) with an alpha-satellite DNA centromeric probe to distinguish between clastogenic and aneugenic effects. Lymphocyte cultures from 32 healthy adults were exposed to 5 and 40 microg/ml HCTZ. Age, gender, and smoking were evaluated as factors affecting the MN analysis. We found that HCTZ increased MN frequencies. FISH analysis revealed that HCTZ exerts its genotoxicity more strongly at the 40 microg/ml concentration, and principally through chromosome delay (aneugenicity). Multiregression analysis of our results confirmed the known effect of age and gender on MN induction in human lymphocytes. Smoking was also a confounding factor for MN induction, especially for centromere-negative MN frequencies. Under the experimental conditions used, only age had a clear positive effect on the response of lymphocytes to HCTZ. These data indicate that HCTZ produces micronuclei in cultured human lymphocytes by a mechanism that involves chromosome delay and to a lesser extent through chromosome breakage.

Thiazide therapy is not a cause of arrhythmia in patients with systemic hypertension.

Forty-four patients with uncomplicated systemic hypertension underwent 48-hour electrocardiographic monitoring before and after four weeks of treatment with hydrochlorothiazide, 100 mg daily. Plasma potassium concentration decreased from 4.07 +/- 0.26 mmol/L (4.07 +/- 0.26 mEq/L) to 3.36 +/- 0.44 mmol/L (3.36 +/- 0.44 mEq/L). The average number of premature ventricular contractions, couplets, or ventricular tachycardia episodes did not change significantly. Twenty patients had more than minimal ventricular ectopy (class 2 to 5) before and 17 after diuretic therapy. Further analysis revealed that following diuretic therapy, neither patients with plasma potassium levels of 3.4 mmol/L or less (less than or equal to 3.4 mEq/L) nor patients with left ventricular hypertrophy had increased ectopy as compared with baseline. At baseline, patients with left ventricular hypertrophy had more arrhythmias than patients without. We conclude that the results of this study provide no evidence that diuretic therapy or diuretic-induced hypokalemia results in increased ventricular ectopy, and that patients with left ventricular hypertrophy may have more ventricular ectopy than patients without, but these arrhythmias are not adversely effected by diuretic therapy.

Diuretic therapy and ventricular arrhythmias in persons 65 years of age and older.

Comparatively high doses of thiazide diuretics have been implicated as a possible cause of ventricular arrhythmias. With the advent of lower recommended dosages, the effect of hydrochlorothiazide 50 mg daily alone and in combination with the potassium-sparing drug, amiloride 5 mg, on the frequency and severity of ventricular arrhythmias was examined in 37 elderly patients. The mean age was 81 +/- 2 years. The study used a randomized, double-blind, crossover design with 3 treatment phases: hydrochlorothiazide, hydrochlorothiazide + amiloride and placebo. A 24-hour Holter monitor recording and serum potassium measurement were obtained at the end of each treatment. Mean serum potassium was significantly (p less than 0.001) reduced with hydrochlorothiazide (3.5 +/- 1 mEq/liter) compared with placebo (4.1 +/- 0.1) and hydrochlorothiazide + amiloride (4.1 +/- 0.1). Serious ventricular arrhythmias occurred in 13 of 37 patients receiving hydrochlorothiazide compared with 15 of 37 receiving placebo and 9 of 37 receiving hydrochlorothiazide + amiloride. Patients who exhibited ventricular ectopy during the placebo phase tended to have an increase in the number of ventricular premature complexes receiving hydrochlorothiazide, although the difference was not statistically significant. There was a significant (p = 0.045) difference in the hourly ventricular premature complex frequency for hydrochlorothiazide compared with hydrochlorothiazide + amiloride. Patients with hypokalemia did not exhibit greater ventricular ectopic activity than those with a normal serum potassium, and concurrent digoxin therapy did not affect arrhythmia occurrence. Hydrochlorothiazide, 50 mg daily, did not affect the frequency or severity of ventricular ectopic activity in this elderly population.

Chronic hydrochlorothiazide and verapamil effects on motor activity in hypertensive baboons.

Spontaneous motor activity was measured in six baboons during chronic oral dosing with a diuretic (hydrochlorothiazide/triamterene), a calcium channel blocker (verapamil), and a combination of the two drugs. Piezoelectric monitors sensitive to movement were attached to leather collars and were worn continuously by the baboons throughout the protocol. Baboons were made hypertensive during a preexperimental period by either 1) chronic administration of deoxycorticosterone acetate (DOCA)-salt or 2) surgical renal artery stenosis. Total inactive periods/day increased over baseline levels during diuretic alone and increased further during diuretic + verapamil combined. The total number of inactive periods/day returned toward baseline levels in the subsequent conditions of verapamil alone and baseline recovery. Activity levels decreased during combination dosing mainly during morning hours (0700-1100 h). Overall changes in activity occurred in the second week of dosing; this time period was found earlier to maximally decrease blood pressure and to impair behavioral performances.

Renal effects of 26-week administration of olmesartan medoxomil/hydrochlorothiazide in rats.

The combination of an angiotensin II type 1 receptor blocker (ARB) and a diuretic is effective clinically in treatment of hypertension. As a non-clinical safety evaluation of a combination of the ARB olmesartan medoxomil (OM) and the diuretic hydrochlorothiazide (HCTZ), male and female normotensive rats were administered OM/HCTZ (fixed ratio of 8 : 5) orally by gavage for 26 weeks at dose levels of 0, 4.88, 16.25, 48.75, 162.5, 487.5, or 1625 mg/kg/day. Additional groups were given 1000 mg/ kg/day OM or 625 mg/kg/day HCTZ. Statistically significant and marked decreases in urinary protein excretion were observed in males and females given doses of 16.25 mg/kg/day or higher compared to vehicle-control groups. Increases in blood urinary nitrogen (BUN) were observed in males and females given doses of 16.25 and 162.5 mg/kg/day or higher, respectively. Increased incidence of chronic progressive nephropathy (CPN), a rat-specific spontaneous renal lesion, was observed in males and females given doses of 48.75 mg/kg/day or higher. An additional mechanistic study, consisting of male and female rats given 0, or 162.5 mg/kg/day OM/HCTZ, was conducted to clarify the toxicological significance of the increases in BUN and the increased incidence of CPN described above. This additional study clearly demonstrated that saline-supplementation through free access to saline in the drinking water ameliorated the elevation in BUN and also ameliorated the incidence of CPN. Consequently, the effects on BUN and CPN observed in the first study can be explained by the hemodynamic disturbances caused by the large doses and an exaggerated pharmacological action in volume-depleted normotensive animals. Importantly, the marked decreases in urinary protein were not affected by the saline-supplementation, and indicated that OM/HCTZ elicited a renoprotective effect, probably by an effect on the glomeruli. An additional toxicokinetic study revealed no drug interactions between OM and HCTZ. In conclusion, OM/HCTZ induced a renoprotective effect as well as changes probably attributed to the exaggerated pharmacological action of the ARB with diuretic in normotensive rats. These results suggest that OM/HCTZ may have renoprotective effects in clinical treatment of hypertensive patients.

[Effect of long-term treatment with propranolol or hydrochlorothiazide on biochemical risk factors of coronary disease in patients with hypertension]. / Wplyw prezewleklego leczenia propranololem lub hydrochlorotiazydem na biochemiczne czynniki zagrozenia choroba wiencowa u chorych na nadcisnienie tetnicze krwi.

In 59 patients with mild or moderate essential hypertension effects of propranolol and hydrochlorothiazide on serum lipids, fibrynogen, glucose and uric acid concentrations as well as serum euglobulins fibrynolysis time were studied. 36 patients received propranolol and 23 subjects hydrochlorothiazide. Follow-up time was 1 year. Statistically significant increases of serum triglycerides, fibrynogen, levels and total cholesterol/HDL cholesterol LDH/HDL indices in comparison with their initial values were stated in a propranolol group. Significant serum cholesterol increase after 6 month therapy was the most substantial metabolic change in a hydrochlorothiazide group. Alterations of lipids indices in both groups were especially intensive in patients with pretreatment stated disturbances of lipids metabolism.

[Hyponatremia--should it be ignored or diagnosed?--Case 8/2011]. / Hyponatriämie--ignorieren oder diagnostizieren?--Fall 8/2011.

UNLABELLED: HISTORY, CLINICAL FINDINGS: A 72-year-old dehydrated female was admitted to our emergency department. She presented with a decreased level of consciousness and had experienced a fall. Her medication included hydrochlorothiazide and amiloride. DIAGNOSTIC: Laboratory findings showed a severe hyponatremia with a serum sodium concentration of 107 mmol/l and a reduced serum osmolality. Urine sodium and potassium excretion were > 30 mmol/l. A CT scan of the head did not show any signs of trauma. DIAGNOSIS, THERAPY AND CLINICAL COURSE: Using a diagnostic algorithm, the diagnosis of a hypotonic hypovolemic hyponatremia due to the intake of diuretics was confirmed. By intravenous infusion of physiological sodium chloride solution and cessation of diuretics, serum sodium concentration was raised gradually. Hereby, the patient`s state of consciousness completely normalized. CONCLUSIONS: Hyponatremia represents the most frequent electrolyte disturbance of hospitalized patients. It correlates with neurological deficits, proneness to falling and intrahospital mortality. Due to diagnostic insecurity of many physicians, the finding of a hyponatremia is often ignored or misclassified. Standardized approaches using diagnostic algorithms improve diagnostic accuracy. The here presented algorithm is based on only few parameters: serum and urine osmolality, urine sodium and potassium. Besides gradual raise of serum sodium, therapy of the underlying cause is essential, for example cessation of diuretics. For patients with syndrome of inadequate secretion of antidiuretic hormone (SIADH; hypotonic isovolemic hyponatremia), selective arginin-vasopressin-receptor 2-antagonists (vaptans) are a new therapeutic option. However, due to high costs, we only see an indication for patients with SIADH who are not able to consequently comply with fluid restriction.

Human renal organic anion transporter 4 operates as an asymmetric urate transporter.

Human organic anion transporter 4 (hOAT4) is located at the apical membrane of proximal tubule cells and involved in renal secretion and reabsorption of endogenous substances as well as many drugs and xenobiotics. This study reevaluated the physiologic role, transport mode, and driving forces of hOAT4. 6-Carboxyfluorescein (6-CF) uptake into HEK293 cells that stably expressed hOAT4 was saturable, resulting in a K(m) of 108 muM. 6-CF as well as [(3)H]estrone sulfate ([(3)H]ES) accumulation by HEK293-hOAT4 cells were abolished by ES, dehydroepiandrosterone sulfate, sulfinpyrazone, benzbromarone, and probenecid, whereas several OA, including p-aminohippurate (PAH), lactate, pyrazinoate, nicotinate, glutarate, and the diuretic hydrochlorothiazide (HCTZ) exhibited a slight or a NS inhibitory effect. PAH and glutarate are not taken up by HEK293-hOAT4 cells, but they trans-stimulated 6-CF and [(3)H]ES uptake, indicating an asymmetric interaction of hOAT4 with these substrates. In chloride-free medium, HEK293-hOAT4-mediated [(3)H]PAH efflux was almost abolished, whereas addition of ES restored it comparable to Ringer solution, consistent with a physiologic ES/PAH or PAH/Cl(-) exchange mode of hOAT4. Moreover, an acidification of the uptake medium increased 6-CF as well as [(3)H]ES uptake, which was reduced by nigericin, suggesting that hOAT4 also can operate as an OA/OH(-) exchanger. hOAT4 facilitates substantial uptake of [(14)C]urate, which was elevated 2.6-fold by intracellular HCTZ. Thus, hOAT4 is the long-postulated, low-affinity apical urate anion exchanger that facilitates HCTZ-associated hyperuricemia.