METHYCLOTHIAZIDE
(meth-i-kloe-thye'a-zide)
Duretic  , Enduron
Classifications: electrolytic and water balance agent; thiazide diuretic; antihypertensive agent
Prototype: Hydrochlorothiazide
Pregnancy Category: C
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2.5 mg, 5 mg tablets
Thiazide diuretic which is similar to hydrochlorothiazide. Diuretic effect results from a drug-induced inhibition of the renal
tubular reabsorption of electrolytes. The excretion of sodium and chloride is enhanced. There is also a loss of potassium
ions via the kidney.
BP is lowered, probably by the loss of sodium and water, and consequently blood volume. Edema is also decreased in CHF patients
by the same mechanism.
Antihypertensive treatment and adjunctively in the management of edema associated with CHF, renal pathology, and hepatic cirrhosis.
Hypersensitivity to thiazides, and sulfonamide derivatives; anuria, hypokalemia, pregnancy (category C), lactation.
Impaired kidney or liver function; gout; SLE; hypercalcemia; diabetes mellitus.
Edema
Adult: PO 2.5–10 mg once/d or 3–5 times/wk
Hypertension
Adult: PO 2.5–10 mg/d
Child: PO 0.05–0.2 mg/kg/d
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Oral
- Give early in a.m. after eating (reduces gastric irritation) to prevent sleep interruption because of diuresis. If 2 doses
are ordered, administer second dose no later than 3 p.m.
- Store at 15°–30° C (59°–86° F) unless otherwise instructed.
Body as a Whole: Postural hypotension, sialadenitis, unusual fatigue, dizziness, paresthesias. Skin: Photosensitivity. Special Senses: Yellow vision. Metabolic: Hypokalemia. Hematologic: Agranulocytosis.
Drug: Amphotericin B, corticosteroids increase hypokalemic effects; may antagonize hypoglycemic effects of insulin, sulfonylureas; cholestyramine, colestipol decrease thiazide absorption; intensifies hypoglycemic and hypotensive effects of diazoxide; increased potassium and magnesium loss may cause digoxin toxicity; decreases lithium excretion, increasing its toxicity; nsaids may attenuate diuresis, and risk of nsaid-induced kidney failure increased.
Absorption: Incompletely absorbed. Onset: 2 h. Peak: 6 h. Duration: >24 h. Distribution: Distributed throughout extracellular tissue; concentrates in kidney; crosses placenta; distributed in breast milk. Metabolism: Does not appear to be metabolized. Elimination: Excreted in urine.
Assessment & Drug Effects
- Expect antihypertensive effects in 3–4 d; maximal effects may require 3–4 wk.
- Monitor BP and I&O ratio during first phase of antihypertensive therapy. Report a sudden fall in BP, which may initiate severe
postural hypotension and potentially dangerous perfusion problems, especially in the extremities.
- Lab tests: Periodic serum electrolytes and CBC with differential.
- Monitor patient for S&S of hypokalemia (see Appendix F). Report promptly. Physician may change dose and institute replacement
therapy.
Patient & Family Education
- Eat a balanced diet to protect against hypokalemia; generally not severe even with long-term therapy. Prevent onset by eating
potassium-rich foods including a banana (about 370 mg potassium) and at least 180 mL (6 oz) orange juice (about 330 mg potassium)
every day.
- Watch carefully for loss of glycemic control (diabetics) and early signs of hyperglycemia (see Appendix F). Symptoms are slow
to develop.
- Avoid OTC drugs unless the physician approves them. Many preparations contain both potassium and sodium, and may induce electrolyte
imbalance adverse effects.
- Older adults are more responsive to excessive diuresis; orthostatic hypotension may be a problem.
- Change positions slowly and in stages from lying down to upright positions; avoid hot baths or showers, extended exposure
to sunlight, and standing still. Accept assistance as necessary to prevent falling.
- Do not drive or engage in potentially hazardous activities until adjustment to the hypotensive effects of drug has been made.
- Do not breast feed while taking this drug.
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Prototype drug