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Hydrochlorothiazide (HCTZ)

Diureticprescriptionoral · inferred

Thiazide diuretic for hypertension and edema. Inhibits sodium-chloride cotransporter in the distal convoluted tubule. Not metabolized; excreted unchanged renally (~61% within 24h). Onset within 2 hours, duration up to 24 hours.

Projected serum levels — 25 mg, once daily

Hydrochlorothiazide (HCTZ)
Hydrochlorothiazide (HCTZ) modeled serum levels, 25 mg once daily over 15 days Population-based pharmacokinetic estimate. Steady state reached after approximately 1 days. 0 5 10 15 20 Day 0 Day 4 Day 8 Day 11 Day 15 Time on a regular schedule ≈ steady state · day 1
Hydrochlorothiazide (HCTZ) modeled serum levels with a loading dose of 31.2 mg, then 25 mg once daily The first dose is larger so levels approach steady state faster. 0 5 10 15 20 Day 0 Day 4 Day 8 Day 11 Day 15 Time on a regular schedule

Maintenance schedule: 25 mg once daily (oral).

Loading schedule: 31.2 mg on day 1, then 25 mg once daily — reaching therapeutic levels sooner.

Modeled steady state after ~1 days: peak ≈ 17.1 mg, trough ≈ 4.0 mg body load. Population-based estimate over 15 days for a 25 mg dose at a 70 kg reference body mass — the interactive app scales curves to your doses, timing, and body mass.

Key facts

Category
Diuretic
Route modeled
Oral
Model confidence
inferred
Half-life
10 h
Common dose
25 mg
Suggested maximum
50 mg/day
Reference dose range
12.5–50 mg (single dose)
Suggested cadence
once daily
Validated against
50 mg oral — Cmax 0.37 mg/L at 2.5 h

Documented interactions

  • warning
    Lithium Orotate (Microdose) + Hydrochlorothiazide (HCTZ) Potentiation

    Thiazide diuretic reduces lithium renal clearance, increasing plasma lithium and toxicity risk.

  • caution
    Aspirin (Acetylsalicylic Acid) + Hydrochlorothiazide (HCTZ) Depletion

    NSAID may reduce thiazide efficacy via prostaglandin inhibition.

  • watch
    Chlorthalidone + Hydrochlorothiazide (HCTZ) Stacked effects

    Chlorthalidone and Hydrochlorothiazide (HCTZ) both push the carbonic anhydrase in the same direction.

Serum checks 3 modeled interaction pairings for hydrochlorothiazide (hctz) across your whole stack — absorption conflicts, enzyme inhibition, and nutrient depletion included.

Research behind this entry

  1. Major outcomes in high-risk hypertensive patients randomized to ACE inhibitor or calcium channel blocker vs diuretic (ALLHAT) ALLHAT Officers and Coordinators · JAMA, 2002 DOI

    Largest hypertension trial (33,357 patients) established thiazide-type diuretics as first-line therapy, with chlorthalidone performing as well or better than amlodipine and lisinopril for cardiovascular outcomes.

  2. Pharmacokinetics of hydrochlorothiazide in man Beermann B, Groschinsky-Grind M · European Journal of Clinical Pharmacology, 1977 DOI

    Foundational pharmacokinetic study establishing HCTZ bioavailability of 60-70%, elimination half-life of 6-15 hours, and renal excretion of unchanged drug as the primary elimination route.

  3. Hydrochlorothiazide vs chlorthalidone, pharmacokinetic and pharmacodynamic differences Ernst ME, Moser M · Hypertension, 2004 DOI

    Critical comparison revealing pharmacokinetic differences between HCTZ (t1/2 ~9h) and chlorthalidone (t1/2 ~45h), suggesting chlorthalidone provides more sustained blood pressure reduction.

3 published studies referenced in the app, each with a plain-language summary.