CLORPRES
Clinical safety rating: caution
Comprehensive clinical and safety monograph for CLORPRES (CLORPRES).
CLORPRES is a combination of clonidine (alpha-2 adrenergic agonist that reduces sympathetic outflow) and chlorthalidone (thiazide diuretic that inhibits sodium reabsorption in distal tubules).
| Metabolism | Clonidine: hepatic metabolism (CYP2D6); Chlorthalidone: excreted unchanged in urine. |
| Excretion | Renal excretion accounts for approximately 50% of elimination, with 30% as unchanged drug and 20% as metabolites; biliary/fecal elimination accounts for about 10%. |
| Half-life | Terminal elimination half-life is 4-6 hours; may be prolonged in renal impairment, requiring dose adjustment. |
| Protein binding | Approximately 90% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | 0.8-1.0 L/kg, indicating extensive tissue distribution; higher Vd may correlate with prolonged effect. |
| Bioavailability | Oral bioavailability is 60-70% due to first-pass metabolism; intravenous bioavailability is 100%. |
| Onset of Action | Oral: 1-2 hours; Intravenous: 5-10 minutes; onset of antihypertensive effect correlates with peak plasma concentrations. |
| Duration of Action | 8-12 hours; clinical effect may persist up to 24 hours due to active metabolites; duration may exceed half-life due to tissue binding. |
One tablet (clonidine 0.1 mg/chlorthalidone 15 mg) orally once or twice daily; maximum 0.6 mg clonidine/90 mg chlorthalidone daily.
| Dosage form | TABLET |
| Renal impairment | Chlorthalidone is ineffective if GFR <30 mL/min; avoid use. Clonidine requires dose reduction when GFR <10 mL/min; start at 0.1 mg once daily. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B: reduce clonidine dose by 25%. Child-Pugh C: avoid or use with extreme caution; clonidine may precipitate encephalopathy. |
| Pediatric use | Not recommended for children; safety and efficacy not established. |
| Geriatric use | Start with clonidine 0.1 mg chlorthalidone 15 mg once daily; monitor for orthostatic hypotension, bradycardia, and electrolyte disturbances. Titrate slowly every 2 weeks. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for CLORPRES (CLORPRES).
| Breastfeeding | Excreted in breast milk. M/P ratio not established. Monitor infant for bradycardia, hypotension, and hypoglycemia. Use caution; alternative agents preferred. |
| Teratogenic Risk | Pregnancy Category C. First trimester: risk of fetal bradycardia, oligohydramnios, and growth restriction due to reduced placental perfusion. Second/third trimester: potential for neonatal hypotension, respiratory depression, and electrolyte disturbances. Avoid use in pregnancy unless benefit outweighs risk. |
| Fetal Monitoring |
■ FDA Black Box Warning
None
| Serious Effects |
["Hypersensitivity to clonidine or chlorthalidone","Anuria","Severe bradycardia or heart block"]
| Precautions | ["Rebound hypertension with abrupt clonidine withdrawal","Hypokalemia due to chlorthalidone","Bradycardia and syncope","Renal impairment: monitor electrolytes"] |
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| Monitor maternal blood pressure, heart rate, and serum electrolytes. Fetal heart rate monitoring for bradycardia. Ultrasound for fetal growth and amniotic fluid index. |
| Fertility Effects | No documented adverse effects on fertility. Limited data; theoretical risk due to hemodynamic changes. |