Quinidine
Contraindicated
Textbook
Fatal ventricular arrhythmias.
Avoid coadministration or ensure strict potassium management.
Source: G&G 14e · p567
Drug reference
Chlorthalidone
Thiazide-like diuretic · Diuretic
Also known as Chlortalidone
START
Baseline electrolytes (Na, K, Mg, uric acid), creatinine, glucose. Check for gout history. In elderly: start 6.25-12.5mg (high hyponatremia risk).
TYPICAL MAX
50mg/day for hypertension; 100mg/day for edema. Higher doses increase metabolic side effects without proportional BP benefit.
STOP IF
Severe hyponatremia (<125 mmol/L), severe hypokalemia (<2.5 mmol/L), acute gout, anuria, severe hepatic impairment, pancreatitis.
WATCH
Electrolytes (Na, K, Mg) at 1-2 weeks, then every 3-6 months. Uric acid (gout risk). Glucose (may worsen glycemic control in diabetics). Renal function. Elderly women at highest hyponatremia risk. Take in morning to avoid nocturia.
CDSCO approvedATC C03BA04
KDIGO 2024 + manufacturer label
- ONSET
- 2.5h · Onset 2-3 hours
- PEAK
- 4h · Tmax 2-6 hours
- t½
- 2.1d · t½ ~40-60 hours
- DURATION
- 2d · 24-72 hours
EXCRETION
Renal unchanged (~65%)
route + CYP
INTERACTIONS
12 major
incl. contraindicated
PREGNANCY
Crosses placenta; may cause fetal electrolyte disturbances, jaundice, thrombocytopenia. Use only if essential—preferred in pregnancy over ACE inhibitors/ARBs for hypertension.
FDA category + note
Top interactionssee all 12 →
- QuinidineContraindicatedTextbookG&G 14e · p567
- CotrimoxazoleSevereTextbook-citedKDT 7e · p948
- SulfonamidesSevereTextbook-citedKDT 7e · p948
- Aminolevulinic AcidSevereDatabaseDDInter
Available in India
54 branded formulations and 55 fixed-dose combinations. Look up specific brands in the Drugs workspace.
Mechanism
Inhibits sodium-chloride cotransporter (NCC) in the distal convoluted tubule, reducing sodium and water reabsorption. Also has vasodilatory effects independent of diuresis. Longer-acting than hydrochlorothiazide.
Indications
Hypertension (first-line, especially in Black patients and elderly)Edema (heart failure, hepatic cirrhosis, renal disease)Prevention of calcium nephrolithiasisDiabetes insipidus (nephrogenic)Osteoporosis (reduces urinary calcium excretion)
Dosing
- Adult
- Hypertension: 12.5-25mg PO daily initially; may increase to 50mg daily. Edema: 50-100mg daily or 100mg every other day. Lower doses (6.25-12.5mg) effective for BP with fewer metabolic side effects.
- Pediatric
- 2mg/kg/day (max 50mg) in single or divided doses.
- Renal adjustment
- CrCl <30: reduced efficacy; loop diuretic preferred. Avoid if CrCl <15.
- Hepatic adjustment
- Use caution; may precipitate hepatic encephalopathy (hypokalemia).
- Geriatric
- Start 6.25-12.5mg daily; increased risk of hyponatremia and hypokalemia; monitor electrolytes closely.
- Max dose
- 100mg/day (edema); 50mg/day (hypertension)
Pharmacokinetics
Onset
2-3 hours
Peak effect
Tmax 2-6 hours; diuretic peak at 4-6 hours; antihypertensive effect over 1-2 weeks
Duration
24-72 hours (much longer than HCTZ)
Half-life
~40-60 hours (long terminal half-life)
Bioavailability
~65%
Protein binding
~75%
Metabolism
Minimal hepatic metabolism
Excretion
~65% unchanged in urine; some biliary/fecal excretion
Contraindications
- Anuria
- Severe renal or hepatic impairment
- Sulfonamide hypersensitivity (relative)
- Hypokalemia
- Hyponatremia
- Gout (acute—may precipitate flare)
Side effects
Common
HypokalemiaHyponatremiaHyperuricemia / goutHyperglycemiaDizziness / orthostatic hypotensionPhotosensitivityImpotence
Serious
- Severe hyponatremia (especially elderly women)
- Severe hypokalemia (arrhythmia risk)
- Acute gout
- Pancreatitis (rare)
- Blood dyscrasias (agranulocytosis, thrombocytopenia—rare)
- Severe hepatic impairment
- Hypomagnesemia
Pregnancy & lactation
Pregnancy
Crosses placenta; may cause fetal electrolyte disturbances, jaundice, thrombocytopenia. Use only if essential—preferred in pregnancy over ACE inhibitors/ARBs for hypertension.
Lactation
Excreted in breast milk in small amounts; may suppress lactation. Generally compatible at low doses; monitor infant for diuresis and electrolyte disturbances.
Drug interactions
Cotrimoxazole
Severe
Textbook-cited
Increased incidence of thrombocytopenia
Avoid concurrent use
Source: KDT 7e · p948
Sulfonamides
Severe
Textbook-cited
Increased incidence of thrombocytopenia
Avoid concurrent use
Source: KDT 7e · p948
Aminolevulinic Acid
Severe
Database
Drug interaction classified as: synergy
Source: DDInter
Amiodarone
Severe
Database
Drug interaction classified as: synergy.
Source: DDInter
Arsenic Trioxide
Severe
Database
Fatal ventricular arrhythmias.
Avoid coadministration or ensure strict potassium management.
Source: DDInter
Cisapride
Severe
Database
Drug interaction classified as: synergy
Source: DDInter
Dofetilide
Severe
Database
Fatal ventricular arrhythmias.
Avoid coadministration or ensure strict potassium management.
Source: DDInter
Dolasetron
Severe
Database
Drug interaction classified as: synergy
Source: DDInter
Dronedarone
Severe
Database
Drug interaction classified as: synergy
Source: DDInter
Droperidol
Severe
Database
Drug interaction classified as: synergy
Source: DDInter
Levacetylmethadol
Severe
Database
Drug interaction classified as: synergy
Source: DDInter
Related guidelines
Ask House about Chlorthalidone
Continue into a citation-backed clinical answer with the drug context already attached.
Sources: KD Tripathi 7e, Goodman & Gilman 14e, Harrison 22e, Katzung·Verified: 2026-05-19 · House clinical team·Cockpit curated: 2026-05-19