Thiazide Diuretics

Question 1

MOA - Thiazide and Thiazide-like (Chlorthalidone)

Answer 1

Inhibits sodium reabsorption in the distal convoluted tubule of the nephron, causing increased excretion of NaCl, water and potassium.

Question 2

Chlorthalidone ✍🏽

Answer 2

Tablet
12.5 - 25 mg daily ✍🏽
(Daily doses > 25 mg/day have limited clinical benefit and increased risk of adverse effects)

Question 3

Hydrochlorothiazide ✍🏽

Answer 3

Tablet, Capsule
12.5 - 50 mg daily ✍🏽
(Daily doses > 50 mg/day have limited clinical benefit and increased risk of adverse effects)

Question 4

Chlorothiazide - Diuril

Answer 4

Oral susp. and inj (IV) - Diuril
500 - 2000 mg daily in 1-2 divided doses

Question 5

Indapamide

Answer 5

Tablet
1.25 - 2.5 mg daily

Question 6

Metolazone

Answer 6

Tablet
2.5 - 5 mg daily

Question 7

SAFETY/SEs/MONITORING - CONTRAINDICATIONS

Answer 7

Hypersensitivity to sulfonamide-derived drugs ✍🏽

Question 8

SAFETY/SEs/MONITORING - WARNINGS

Answer 8

Severe renal disease
Progressive liver disease
Transient myopia or acute angle closure glaucoma
Can precipitate or EXACERBATE✍🏽 conditions like SLE, gout, dyslipidemia, and DM ✍🏽

Question 9

SAFETY/SEs/MONITORING - SEs

Answer 9

Decreased electrolytes; K+, Mg, Na ✍🏽
Increased electrolytes/labs; Ca, UA, LDL, TG, BG ✍🏽
Photosensitivity (including a small increased risk of non-melanoma skin cancer ✍🏽
Impotence, dizziness, rash ✍🏽

Question 10

MONITORING

Answer 10

Electrolyte, renal function ✍🏽, BP, fluid status (input and output, weight), BG (in DM)

Question 11

NOTES

Answer 11

Thiazide diuretic effect ✍🏽 is diminished ✍🏽 when CrCl < 30 mL/min ✍🏽 (except METOLAZONE, which is indicated for volume overload in combo with a loop diuretic)

Take early in the day to avoid nocturia ✍🏽

Chlorothiazide is the only thiazide diuretic available in IV ✍🏽

Chlorthalidone is considered more effective at lowering BP due to a longer duration of action and increased potency.

Hypokalemia can be avoided with regular intake of potassium-rich foods, potassium supplements, or concurrent use of a potassium-sparing diuretic.

Question 12

DDIs

Answer 12

Drugs that can cause sodium and water retention - NSAIDS ✍🏽 can decrease thiazide diuretic effectiveness ✍🏽
Monitor BP closely if used in combo. Avoid NSAIDs in CVD patients if possible.

Thiazide diuretics can decrease lithium renal clearance and increase the risk of lithium toxicity. Consider decreasing the lithium dose if a thiazide diuretic is initiated, and monitor lithium levels closely during concurrent treatment.

Thiazide diuretics can increase dofetilide serum concentrations, leading to an increased risk of QT prolongation; do not use in combination. ✍🏽