ANHYDRON
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ANHYDRON (ANHYDRON).
Inhibits the sodium-potassium-2 chloride (Na-K-2Cl) cotransporter in the thick ascending limb of the loop of Henle, reducing reabsorption of sodium, chloride, and potassium, leading to increased urine output.
| Metabolism | Partially metabolized by the liver; primarily excreted unchanged in urine. |
| Excretion | Renal: ~60% unchanged; biliary/fecal: ~40% as metabolites and unchanged drug. |
| Half-life | Terminal elimination half-life is 60-90 minutes, prolonged in renal impairment (up to 24 hours). |
| Protein binding | 95% bound, primarily to albumin. |
| Volume of Distribution | 0.2-0.3 L/kg, reflecting distribution primarily in extracellular fluid. |
| Bioavailability | Oral: ~65% (range 50-80%) due to first-pass metabolism. |
| Onset of Action | Oral: 30-60 minutes; intravenous: 5-15 minutes. |
| Duration of Action | Oral: 6-12 hours; intravenous: 2-4 hours. Duration is dose-dependent and may be shorter in high-output states. |
Oral: 25-100 mg once daily in the morning, or 50-100 mg every other day; maximum 200 mg/day.
| Dosage form | TABLET |
| Renal impairment | GFR 10-50 mL/min: 50 mg every 12 hours. GFR <10 mL/min: 50 mg every 24 hours or not recommended. |
| Liver impairment | Mild to moderate hepatic impairment (Child-Pugh A or B): no adjustment. Severe hepatic impairment (Child-Pugh C): avoid use. |
| Pediatric use | 1-2 mg/kg/dose once daily; maximum 100 mg/day. |
| Geriatric use | Start at 12.5-25 mg once daily; titrate slowly due to risk of hypotension and electrolyte imbalance. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ANHYDRON (ANHYDRON).
| Breastfeeding | Cyclothiazide is excreted into human breast milk. The milk-to-plasma ratio is not well defined for cyclothiazide but for thiazides generally is around 0.5-1.0. May suppress lactation. Potential for infant adverse effects (e.g., electrolyte disturbances, thrombocytopenia). Use caution in breastfeeding; alternatives are preferred. |
| Teratogenic Risk | Cyclothiazide (ANHYDRON) is a thiazide diuretic. Use in pregnancy is generally avoided due to potential adverse effects. First trimester: limited data, but thiazides have been associated with an increased risk of congenital anomalies in some studies, including cleft lip/palate and cardiac defects. Second and third trimesters: can cause fetal or neonatal jaundice, thrombocytopenia, electrolyte disturbances, and possibly intrauterine growth restriction. Crosses the placenta. Use only if clearly needed for maternal conditions like hypertension or edema. |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
["Anuria","Severe renal failure","Hepatic coma or pre-coma","Severe electrolyte depletion","Hypersensitivity to sulfonamides"]
| Precautions | ["Electrolyte imbalance (hypokalemia, hyponatremia, hypochloremia)","Dehydration and hypotension","Ototoxicity (especially with rapid IV administration or renal impairment)","Hyperuricemia and gout","Sulfonamide cross-sensitivity in sulfa-allergic patients"] |
| Food/Dietary | Avoid excessive intake of potassium-rich foods (e.g., bananas, oranges, spinach) as hyperkalemia may occur. Limit salt substitutes containing potassium. Grapefruit juice may increase drug absorption; avoid concurrent use. Alcohol may enhance orthostatic hypotension. |
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| Fetal Monitoring | Monitor maternal blood pressure, serum electrolytes (especially potassium, sodium, chloride, calcium), renal function (BUN, creatinine), and blood glucose (can increase glucose levels). Fetal monitoring: ultrasound for growth and amniotic fluid volume; periodic non-stress test or biophysical profile in third trimester if used for hypertension. Neonatal monitoring for jaundice, thrombocytopenia, and electrolyte imbalance. |
| Fertility Effects | Thiazide diuretics may have minimal effects on fertility. No specific data for cyclothiazide. In males, no known effects on spermatogenesis. In females, may affect ovulation due to volume depletion or electrolyte changes, but not well documented. |
| Clinical Pearls | ANHYDRON (cyclothiazide) is a thiazide-like diuretic used for hypertension and edema. Monitor serum potassium and glucose levels; hypokalemia and hyperglycemia are common. Use with caution in renal impairment (CrCl <30 mL/min). Avoid in patients with anuria or sulfonamide allergy. |
| Patient Advice | Take exactly as prescribed, usually once daily in the morning to avoid nighttime urination. · May cause dizziness or lightheadedness; rise slowly from sitting or lying down. · Avoid prolonged sun exposure; use sunscreen as photosensitivity may occur. · Report signs of electrolyte imbalance: muscle cramps, weakness, irregular heartbeat. · Do not stop abruptly without consulting your doctor; gradual dose reduction may be needed. |