ORETIC
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ORETIC (ORETIC).
Hydrochlorothiazide inhibits the sodium-chloride symporter in the distal convoluted tubule of the nephron, reducing reabsorption of sodium and chloride, leading to increased excretion of water and electrolytes.
| Metabolism | Hydrochlorothiazide is not extensively metabolized; the majority is excreted unchanged in urine. |
| Excretion | Renal: approximately 95% (primarily as unchanged drug via tubular secretion), Biliary/fecal: <5% |
| Half-life | Terminal elimination half-life: 6-15 hours (average 10 hours); prolonged in renal impairment and heart failure; clinical context: duration of diuretic effect correlates with half-life, requiring once or twice daily dosing. |
| Protein binding | Approximately 95% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | Vd: 0.2-0.4 L/kg; indicates distribution primarily in extracellular fluid and limited tissue penetration. |
| Bioavailability | Oral bioavailability: approximately 65-70% (range 50-80%) with significant interindividual variability due to first-pass metabolism and food effects. |
| Onset of Action | Oral: diuresis begins within 2 hours; peak effect at 4-6 hours. Intravenous: onset within 15-30 minutes. |
| Duration of Action | Oral: approximately 6-12 hours; duration of diuretic effect is dose-dependent and may be extended in renal impairment. Intravenous: diuresis lasts 2-4 hours. |
| Molecular Weight | 295.36 |
25-100 mg orally once or twice daily; maximum 200 mg/day.
| Dosage form | TABLET |
| Renal impairment | GFR 10-50 mL/min: 50 mg orally every 12 hours; GFR <10 mL/min: avoid or use 50 mg orally every 24 hours. |
| Liver impairment | Child-Pugh Class A: no adjustment; Class B: reduce dose by 50%; Class C: avoid use. |
| Pediatric use | 1-2 mg/kg orally once daily; maximum 50 mg/day for children <12 years. |
| Geriatric use | Start at 12.5-25 mg orally once daily; adjust slowly to avoid hypotension and electrolyte imbalance. |
| 1st trimester | Avoid: Associated with oligohydramnios, fetal limb reduction defects, and neonatal jaundice. Use only if no safer alternative. |
| 2nd trimester | Use with caution: May cause fetal/neonatal electrolyte disturbances, jaundice, and thrombocytopenia. Monitor fetal growth. |
| 3rd trimester | Use with caution: Risk of neonatal hypoglycemia, electrolyte imbalances, and jaundice. Discontinue before delivery if possible. |
Clinical note
Comprehensive clinical and safety monograph for ORETIC (ORETIC).
| Placental transfer | Crosses placenta; achieves fetal concentrations similar to maternal levels. |
| Breastfeeding | Excreted in breast milk in low amounts; may suppress lactation, especially with higher doses. Monitor infant for electrolyte disturbances and jaundice. Consider alternative if high doses required or infant is premature/ill. |
■ FDA Black Box Warning
None
| Serious Effects |
AnuriaHypersensitivity to hydrochlorothiazide or sulfonamide derivatives
| Precautions | Hypokalemia: Monitor potassium levels and supplement if necessary., Hypomagnesemia: May occur, especially with prolonged use., Hyperuricemia: May precipitate gout attacks., Sulfonamide allergy: Cross-sensitivity may occur in patients with sulfonamide allergy., Systemic lupus erythematosus: May exacerbate or activate SLE., Impaired renal function: Use with caution; may accumulate in severe renal impairment. |
| Food/Dietary | Avoid excessive sodium intake; use salt substitutes cautiously due to potassium content. Grapefruit juice may increase hydrochlorothiazide levels. Alcohol can potentiate hypotension. Avoid large amounts of potassium-rich foods if on potassium supplements or ACE inhibitors. |
Loading safety data…
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | FDA Pregnancy Category C. First trimester: No adequate studies; potential risk based on animal data. Second/third trimesters: Possible fetal/neonatal adverse effects including jaundice, thrombocytopenia, electrolyte disturbances. Avoid for pregnancy-induced hypertension or preeclampsia as it may decrease placental perfusion. |
| Fetal Monitoring | Monitor maternal blood pressure, serum electrolytes (especially potassium), uric acid, renal function. Fetal: Periodic ultrasound for growth, amniotic fluid volume. Neonatal: Observe for hypoglycemia, electrolyte abnormalities, thrombocytopenia. |
| Fertility Effects | No direct evidence of impaired fertility in humans. Animal studies show no significant adverse effects. May disturb electrolyte and hormonal balance affecting menstrual cycle. Use in pre-existing hypertension may improve fertility outcomes if blood pressure controlled. |
| Clinical Pearls | ORETIC (hydrochlorothiazide) is a thiazide diuretic. Monitor serum potassium and glucose, especially in diabetic patients. Use cautiously in patients with renal impairment (CrCl <30 mL/min is relative contraindication). Can exacerbate gout by increasing serum uric acid. Onset of diuresis is 2 hours, peak at 4-6 hours, duration 6-12 hours. |
| Patient Advice | Take in the morning to avoid nocturia. · May cause dizziness due to dehydration; rise slowly from sitting or lying down. · Avoid prolonged sun exposure; use sunscreen as this drug can increase photosensitivity. · Report symptoms of electrolyte imbalance: muscle cramps, weakness, irregular heartbeat, excessive thirst. · Do not consume grapefruit juice as it may increase drug levels and risk of side effects. |