Hydrochlorothiazide dosage

Some pharmacokinetic characteristics and the initial and usual maintenance dosages of hydrochlorothiazide are listed in Table 11-2. Although thiazide diuretics are more natriuretic at higher doses (up to 100-200 mg of hydrochlorothiazide), when used as a single agent, lower doses (25-50 mg) exert as much antihypertensive effect as do higher doses. In contrast to thiazides, the blood pressure response to loop diuretics continues to increase at doses many times greater than the usual therapeutic dose. 

Furosemide and thiazide diuretics (Fig. 8.4) have been approved for use in dairy cattle for treatment of postparturient edema of the mammary gland and associated structures (56). Furosemide and hydrochlorothiazide are administered intramuscularly or intravenously at a dosage of 500 and 125-250 mg/animal, respectively. Chlorothiazide and trichlormetliiazide are administered orally at dosage of 2000 and 200 mg/animal, respectively. 

Trichlormethiazide is often given in combination with dexamethasone because in this way effects can be achieved with a minimum dosage of trichlormethiazide, since tire two drugs are complementary in their action. Studies in humans and experimental animals have shown that trichlormethiazide presents a favorable pattern of lower potassium excretion than the other thiazides. The clinically determined saluretic potency of trichlormethiazide was estimated to be 10-20 times lower than that of hydrochlorothiazide and 100-200 times lower than that of chlorothiazide this results in decrease in the incidence of hypokalemic manifestations. 

Trade Name Potassium-Sparing Agent Hydrochlorothiazide Frequency of Dosage... 

G. Ramana Rao, G. Raghuveer, and P. Khadgapathi, High-performance liquid chromatographic determination of metoprolol tartrate and hydrochlorothiazide in dosage forms, Indian Drugs, 25 39(1985). 

Panderi and Parissi-Poulou developed a microbore liquid chromatographic method for the simultaneous determination of benazepril hydrochloride and hydrochlorothiazide in pharmaceutical dosage forms [30]. The use of a BDS C-18 microbore analytical column was found to result in substantial reduction in solvent consumption and in increased sensitivity. The mobile phase consisted of a mixture of 25 mM sodium dihydrogen phosphate buffer (pH 4.8) and acetonitrile (11 9 v/v), pumped at a flow rate of 0.4 mL/min. Detection was effected at 250 nm using an ultraviolet absorbance detector. The intra- and inter-day relative standard deviation values were less than 1.25% (n = 5), while the relative percentage error was less than 0.9% (n = 5). The detection limits obtained according to the IUPAC definition were 0.88 and 0.58 pg/mL for benazepril hydrochloride and hydrochlorothiazide, respectively. The method was applied to the quality control of commercial tablets and content uniformity test, and proved to be suitable for rapid and reliable analysis. 

Hassib et al. developed two chromatographic procedures for the simultaneous determination of benazepril hydrochloride and hydrochlorothiazide in laboratory made mixtures, and in pharmaceutical dosage forms (Cibadrex tablets) using reversed phase HPLC and TLC methods [24]. For reversed phase HPLC, a very sensitive, rapid, and selective method was developed. The linearity ranges were 32-448 ng/ 20 pL and 40-560 ng/20 pL for benazepril hydrochloride and hydrochlorothiazide, respectively. The corresponding recoveries were 99.38 1.526 and 99.2 1.123. The minimum detection limits were 7 ng/20 pL for benazepril and 14 ng/20 pL for hydrochlorothiazide. The method could be successfully applied for the determination of laboratory made mixtures and for pharmaceutical dosage forms. The results obtained were compared with those obtained by a spectrophotometric method. 

A 69-year-old woman took terbinafine 250 mg/day for 112 days for subungual hyperkeratosis and developed hair loss after 3 months. She was also taking hydrochlorothiazide, amiloride hydrochloride, and amlodi-pine besilate, all in the same dosage for more than 5 years. Clinical and laboratory investigations showed no other obvious causes, and hair loss completely reversed on withdrawal of terbinafine. 

Methyidopa is available in an oral dosage form (alone or in combination with a thiazide diuretic, hydrochlorothiazide) and a parenteral dosage form (methyldopate hydrochloride). 

The manufacturer notes that, in 13 healthy subjects, hydrochlorothiazide 50 mg daily increased the AUC and plasma levels of fluconazole 100 mg daily for 10 days by about 40%. They attribute these changes to a reduction in the renal clearance of fluconazole. However they say it is unlikely that a change in the fluconazole dosage will be needed in patients taking diuretics, but that the interaction should be borne in mind. Any interaction is almost certainly of no relevance in patients taking a single dose of fluconazole for genital candidiasis. 

The manufacturers say that amlodipine has been safely given with thiazide diuretics and no dosage adjustment of amlodipine is required. Additive antihypertensive effects are expected when diuretics such as hydrochlorothiazide are used in combination with calcium-channel blockers, and such combinations are used clinically. 

Thiazide and reiated diuretics can cause a rapid rise in serum-iithium ieveis, ieading to toxicity uniess the iithium dosage is reduced appropriateiy. This interaction has been seen with bendroflumethiazide, chiorothiazide, chiortaiidone, hydrochlorothiazide and indapamide, and potentially occurs with hydroflumethiazide. Other thiazides and related diuretics are expected to behave similarly. 

Ramesh, B., Hari babu, K., Sarma, V.U.M., and Devi, PS. 2011. Development and validation of a HPTLC-ESI/MS method for the simultaneous determination of ramipril, hydrochlorothiazide and tehnisartan in tablet dosage form, J. Pharm. Res., 4 4541-4545. 

The importance of dosage form is illustrated where tablets containing triamterene and hydrochlorothiazide caused approximately twice as much excretion of hydrochlorothiazide and three times as much tri-... 

Erk, N. Simultaneous analysis of candesartan cilexetil and hydrochlorothiazide in human plasma and dosage forms using HPLC with a photodiode array detector, J.Liq.Chromatogr.Rel.Technol.y 2003, 26, 2581-2591. 

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