Polythiazide
Pronunciation
(pol i THYE a zide)
U.S. Brand Names
Renese®
Generic Available
No
Use
Adjunctive therapy in treatment of edema and hypertension
Pregnancy Risk Factor
D
Contraindications
Hypersensitivity to polythiazide, any other sulfonamide-derived drugs, or any component of the formulation; anuria; renal decompensation; pregnancy
Warnings/Precautions
Avoid in severe renal disease (ineffective). Electrolyte disturbances (hypokalemia, hypochloremic alkalosis, hyponatremia) can occur. Use with caution in severe hepatic dysfunction; hepatic encephalopathy can be caused by electrolyte disturbances. Gout can be precipitated in certain patients with a history of gout, a familial predisposition to gout, or chronic renal failure. Cautious use in diabetics; may see a change in glucose control. Hypersensitivity reactions can occur. Can cause SLE exacerbation or activation. Use with caution in patients with moderate or high cholesterol concentrations. Photosensitization may occur. Correct hypokalemia before initiating therapy.
Chemical similarities are present among sulfonamides, sulfonylureas, carbonic anhydrase inhibitors, thiazides, and loop diuretics (except ethacrynic acid). Use in patients with sulfonamide allergy is specifically contraindicated in product labeling, however, a risk of cross-reaction exists in patients with allergy to any of these compounds; avoid use when previous reaction has been severe.
Adverse Reactions
1% to 10%: Hypokalemia
<1% (Limited to important or life-threatening): Anorexia, blood dyscrasias (rarely), drowsiness, hepatitis, hypotension; fluid and electrolyte imbalances (hypercalcemia, hypocalcemia, hypomagnesemia, hyponatremia); hyperglycemia, nausea, pancreatitis, photosensitivity, polyuria, prerenal azotemia, rash, uremia, vomiting
Drug Interactions
ACE inhibitors: Increased hypotension if aggressively diuresed with a thiazide diuretic.
Beta-blockers increase hyperglycemic effects in type 2 diabetes mellitus (noninsulin dependent, NIDDM)
Cyclosporine and thiazides can increase the risk of gout or renal toxicity; avoid concurrent use.
Digoxin toxicity can be exacerbated if a thiazide induces hypokalemia or hypomagnesemia.
Lithium toxicity can occur by reducing renal excretion of lithium; monitor lithium concentration and adjust as needed.
Neuromuscular blocking agents can prolong blockade; monitor serum potassium and neuromuscular status.
NSAIDs may decrease the efficacy of thiazides reducing the diuretic and antihypertensive effects.
Mechanism of Action
The diuretic mechanism of action of the thiazides is primarily inhibition of sodium, chloride, and water reabsorption in the renal distal tubules, thereby producing diuresis with a resultant reduction in plasma volume. The antihypertensive mechanism of action of the thiazides is unknown. It is known that doses of thiazides produce greater reductions in blood pressure than equivalent diuretic doses of loop diuretics (eg, furosemide). There has been speculation that the thiazides may have some influence on vascular tone mediated through sodium depletion, but this remains to be proven.
Pharmacodynamics/Kinetics
Onset of action: Diuresis: ~2 hours
Duration: 24-48 hours
Dosage
Adults: Oral:
Edema: 1-4 mg/day
Hypertension: 2-4 mg/day
Patient Education
May be taken with food or milk; take early in day to avoid nocturia; take the last dose of multiple doses no later than 6 PM unless instructed otherwise. A few people who take this medication become more sensitive to sunlight and may experience skin rash, redness, itching, or severe sunburn, especially if sunblock SPF
15 is not used on exposed skin areas.
Nursing Implications
Monitor blood pressure, fluids, weight loss, serum potassium
Cardiovascular Considerations
Thiazide diuretics are effective first-line therapeutic agents in the management of hypertension and have proven to be of benefit in terms of cardiovascular outcome. They may act synergistically to lower blood pressure when combined with an ACE inhibitor or beta-blocker. The initial concern about thiazide diuretic-induced hypokalemia, glucose intolerance, and lipid profiles does not appear to be of substantial clinical consequence in the treatment of hypertension. The benefits of this class of agents in the treatment of hypertension is established and compares well with other first-line therapeutic agents.
Diuretics are standard therapy for the management of edema in patients with heart failure. However, it is important to ensure that edema is not secondary to pericardial constriction or pericardial effusion. Marked reduction in intravascular volume, with consequent decreased cardiac filling pressures, may precipitate significant hypotension in these circumstances.
Dental Health: Effects on Dental Treatment
No significant effects or complications reported
Dental Health: Vasoconstrictor/Local Anesthetic Precautions
No information available to require special precautions
Mental Health: Effects on Mental Status
May cause drowsiness
Mental Health: Effects on Psychiatric Treatment
May decrease lithium clearance resulting in an increase in serum lithium levels and potential lithium toxicity; monitor serum lithium levels
Dosage Forms
Tablet: 2 mg
References
Chobanian AV, Bakris GL, Black HR, et al, "The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure: The JNC 7 Report,"JAMA, 2003, 289(19):2560-71.
International Brand Names
Nephril® (GB); Renese® (BE, LU)