====== Chlorthalidone (Thalitone®) ======

<WRAP right 340px>
<WRAP infobox>
^ Chlorthalidone | {{ :cardio:diuretics:chlortalidone.svg?150 |}} |
| Brand Name | Thalitone® |
| Drug Class | [[cardio:diuretics:start|Thiazide-like Diuretic]] |
| Primary Indication | Hypertension |
| Site of Action | Distal Convoluted Tubule |
| Mechanism | Na⁺/Cl⁻ Cotransporter Inhibition |
| Potassium Effect | ↓ (Hypokalemia risk) |
| Calcium Effect | ↑ Reabsorption |
| Half-Life | ~40–60 hours |
| Landmark Trial | ALLHAT |
| FDA Approval | 1960 |
</WRAP>
</WRAP>

===== Overview =====

Chlorthalidone is a thiazide-like diuretic used primarily for the treatment of hypertension.

Although often grouped with thiazides, chlorthalidone has a significantly longer half-life and stronger outcome data compared to [[cardio:diuretics:hydrochlorothiazide|Hydrochlorothiazide]].

It is frequently preferred in hypertension guidelines due to its durable 24-hour blood pressure control and cardiovascular outcome benefit.

<WRAP clear></WRAP>

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===== Mechanism of Action =====

**Site of Action**
  * Distal convoluted tubule  

**Transporter Blocked**
  * Na⁺/Cl⁻ cotransporter (NCC)  

**Physiologic Effects**
  * ↑ Sodium and water excretion  
  * ↑ Potassium excretion  
  * ↑ Calcium reabsorption  
  * ↓ Plasma volume  
  * ↓ Peripheral vascular resistance (long-term effect)  

Net effect:
  * Sustained blood pressure reduction  

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===== Indications =====

  * Primary hypertension  
  * Edema (less commonly)  

Supported by:
  * ALLHAT trial — reduction in cardiovascular events  

Often combined with:
  * [[cardio:raas:acei|ACE inhibitors]]  
  * [[cardio:raas:arb|ARBs]]  
  * [[cardio:beta_blockers:start|Beta-blockers]]  

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<WRAP contra>
===== Contraindications =====

Absolute:
  * Anuria  

Relative / Caution:
  * Severe renal impairment (reduced efficacy when eGFR < 30)  
  * Gout  
  * Hyponatremia  
  * Hypokalemia  
  * Diabetes mellitus  

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<WRAP details>
===== Dosing =====

Hypertension:
  * 12.5–25 mg once daily  

Higher doses:
  * Increase metabolic side effects  
  * Provide minimal additional BP reduction  

Long half-life supports once-daily dosing with sustained effect.

</WRAP>

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<WRAP details>
===== Pharmacokinetics =====

Absorption:
  * Oral  

Half-life:
  * ~40–60 hours  

Duration:
  * >24-hour BP control  

Elimination:
  * Renal  

Longer duration compared to hydrochlorothiazide.

</WRAP>

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<WRAP details>
===== Adverse Effects =====

Electrolyte:
  * Hypokalemia  
  * Hyponatremia  
  * Hypomagnesemia  
  * Hypercalcemia  

Metabolic:
  * Hyperglycemia  
  * Hyperuricemia (gout)  
  * Mild dyslipidemia  

Other:
  * Photosensitivity  

Electrolyte abnormalities may be more pronounced than with HCTZ.

</WRAP>

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<WRAP details>
===== Drug Interactions =====

Lithium:
  * Increased lithium levels  

RAAS inhibitors:
  * May blunt potassium loss  

Loop diuretics:
  * Additive electrolyte depletion  

</WRAP>

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<WRAP monitoring>
===== Monitoring =====

  * Blood pressure  
  * Electrolytes (Na⁺, K⁺)  
  * Renal function  
  * Uric acid (if gout risk)  
  * Glucose (diabetics)  

</WRAP>

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<WRAP pearls>
===== Clinical Pearls =====

  * Longer half-life than hydrochlorothiazide.  
  * Strong cardiovascular outcome data (ALLHAT).  
  * Often preferred thiazide for hypertension.  
  * More sustained 24-hour BP control.  
  * Greater risk of electrolyte abnormalities than HCTZ.  

</WRAP>

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===== Comparison Within Class =====

Compared to [[cardio:diuretics:hydrochlorothiazide|Hydrochlorothiazide]]:
  * Longer half-life  
  * Better cardiovascular outcome data  
  * More potent  

Compared to [[cardio:diuretics:indapamide|Indapamide]]:
  * Similar mechanism  
  * Slightly different metabolic profile  

Compared to [[cardio:diuretics:furosemide|Furosemide]]:
  * Less potent diuretic  
  * Not effective in severe renal failure  

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===== Related =====

  * [[cardio:diuretics:start|Diuretics]]
  * [[cardio:diuretics:hydrochlorothiazide|Hydrochlorothiazide]]
  * [[cardio:hypertension:start|Hypertension]]
  * [[cardio:raas:acei|ACE Inhibitors]]