Microzide
Hydrochlorothiazide-induced 131I excretion facilitated by salt and water.

Beyer KH Jr, Fehr DM, Gelarden RT, White WJ, Lang CM, Vesell ES.

Salt intake is restricted under clinical conditions for which thiazide diuretics are customarily used. Dietary iodide intake offsets any effect of thiazide on iodide loss. However, our correlation coefficients relating Na+ to Cl- to I- excretion indicate that as thiazide administration or sodium chloride intake increases renal Na+ and Cl- excretion, I- reabsorption by the nephron coordinately decreases. Increased sodium chloride and water intake by the dog doubled I-excretion rates. Hydrochlorothiazide increased the sodium chloride and water enhanced I-excretion rate as much as eight-fold. Without added NaCl, hydrochlorothiazide increased the excretion rate of 131I by three- to eightfold, acutely. Within five to seven days after 131I oral administration, hydrochlorothiazide (1 or 2 mg/kg twice daily) doubled the rate of 131I disappearance from plasma, reduced the fecal output of 131I, and increased its rate of renal excretion. When hydrochlorothiazide was administered, as much 131I was excreted in the first 24 hours as occurred in 48 hours when sodium chloride and water were given without hydrochlorothiazide. Thiazide administration in customary clinical dosage twice a day with substantial sodium chloride and water for the first two days after exposure to 131I, should therefore facilitate the safe excretion of 131I. This accelerated removal of 131I might be enhanced even more if thyroid uptake of 131I is blocked by administration of potassium iodide, as judged by the greater 131I recovery from thyroidectomized dogs.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7263913&dopt=Abstract hydrochlorothiazide Microzide



Microzide
High-pressure liquid chromatographic determination of chlorothiazide and hydrochlorothiazide in plasma and urine: preliminary results of clinical studies.

Barbhaiya RH, Phillips TA, Welling PG.

High-pressure liquid chromatographic procedures were developed for the determination of chlorothiazide and hydrochlorothiazide in plasma and urine. The plasma assay incorporates a preextraction procedure that eliminates interference by endogenous substances. Chromatography is carried out on an octadecyl reversed-phase column. Mobile phases are 15% methanol in 0.01 M acetic acid for plasma and 4% acetonitrile in 0.01 M sodium perchlorate, adjusted to pH 4.6, for urine. At a flow rate of 2.5 ml/min, the retention times for chlorothiazide and hydrochlorothiazide are 3.5 and 4.6 min for plasma and 10.5 and 13.5 min for urine, respectively. Preliminary results of a clinical study in fasting male volunteers showed that the plasma levels and urinary excretion rate of chlorothiazide peaked at 1-2 hr following a 500-mg oral dose and subsequently declined irregularly. On the other hand, the plasma levels and urinary excretion rate of hydrochlorothiazide peaked at 2-3 hr following a 50-mg oral dose and subsequently declined in biphasic fashion. Urinary excretion rates of both chlorothiazide and hydrochlorothiazide closely resemble their concentration profiles in plasma.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7264894&dopt=Abstract hydrochlorothiazide Microzide



Microzide
In vitro detection of possible in vivo drug interactions. Part 2: A study of the effect of hydrochlorothiazide and frusemide on the partition coefficient and solubility characteristics of propranolol hydrochloride.

Al-Janabi II, Anber SA, Fikrat HT.

The apparent partition coefficient (Kapp.) of propranolol hydrochloride alone and in the presence of hydrochlorothiazide and frusemide were determined between chloroform and artificial intestinal juice. Both diuretics significantly reduced the relatively high Kapp. of propranolol hydrochloride. On the other hand, the relatively low Kapp. of both diuretics were significantly increased by the presence of propranolol hydrochloride. Also in vitro solubility studies were carried out using the Sartorius solubility simulator. The frequently prescribed therapeutic combination of propranolol hydrochloride tablets and either hydrochlorothiazide or frusemide tablets seems, on the whole to have similar in vitro solubility patterns when compared to those of the individual drugs. However, the mutual effects on the apparent partition coefficient revealed in the present work can be one of the factors responsible for improving the in vitro absorption of propranolol hydrochloride and the diuretics when present together.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7280000&dopt=Abstract hydrochlorothiazide Microzide



Microzide
Prevention of calcium nephrolithiasis with low-dose thiazide, amiloride and allopurinol.

Maschio G, Tessitore N, D'Angelo A, Fabris A, Pagano F, Tasca A, Graziani G, Aroldi A, Surian M, Colussi G, Mandressi A, Trinchieri A, Rocco F, Ponticelli C, Minetti L.

We report 5 years' experience with low-dose hydrochlorothiazide, 50 mg/day and amiloride, 5 mg/day, in 519 patients with recurrent calcium nephrolithiasis. Additional treatment with allopurinol, 100 mg/day was prescribed for approximately 50 percent of the patients. All patients had active stone formation, having 3,464 stones in 3,126 patient-years (6.67 stones per patient, 1.10 stones per year). Hypercalciuria was present in 65 percent of the patients and hyperuricosuria in 24 percent. The administration of low-dose hydrochlorothiazide was effective in reducing urinary calcium excretion in most patients. It is possible that the hypocalciuric effect of hydrochlorothiazide were enhanced by amiloride, an agent which has been shown to cause hypocalciuria when given alone. Significant side effects requiring discontinuation of the drug were observed in only 5 percent of the patients. During 872.8 patient-years of treatment, only 53 new stones were formed (0.10 stones per patient, 0.06 stones per year) in contrast with the 916 predicted ones. The difference (chi-square) is statistically significant (p less than 0.001). These results show that the administration of low-dose hydrochlorothiazide and amiloride, either alone or in association with allopurinol, is clinically effective in reducing the rate of recurrence of calcium nephrolithiasis.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7282751&dopt=Abstract hydrochlorothiazide Microzide



Microzide
A comparison of chlorthalidone-reserpine and hydrochlorothiazide-methyldopa as step 2 therapy for hypertension.

Channick BJ, Kessler WB, Marks AD, Adlin EV.

Two fixed-combination drugs commonly used in the step 2 treatment of hypertension, chlorthalidone plus reserpine and hydrochlorothiazide plus methyldopa, were compared in an evaluation of efficacy and adverse reactions. Ninety-one percent of the chlorthalidone-reserpine group achieved diastolic blood pressures of 90 mmHg or lower compared with 55% of the hydrochlorothiazide-methyldopa group. The incidence of adverse reactions in the chlorthalidone-reserpine group was 31% compared with an incidence of 64% in the hydrochlorothiazide-methyldopa group.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7307035&dopt=Abstract hydrochlorothiazide Microzide