Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
CATAPRES-TTS-2 vs CATAPRES-TTS-3
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Clonidine is a centrally acting alpha-2 adrenergic agonist that stimulates alpha-2 adrenergic receptors in the brainstem, activating inhibitory neurons and reducing sympathetic outflow from the central nervous system, resulting in decreased peripheral vascular resistance, heart rate, and blood pressure.
Clonidine is an alpha-2 adrenergic agonist that reduces sympathetic outflow from the central nervous system, resulting in decreased peripheral vascular resistance, decreased heart rate, and lowered blood pressure.
Hypertension (alone or in combination with other antihypertensive agents),Off-label: Attention deficit hyperactivity disorder (ADHD), menopausal hot flashes, opioid withdrawal, migraine prophylaxis, Tourette syndrome
Hypertension (first-line treatment),Off-label: Attention deficit hyperactivity disorder (ADHD), management of opioid withdrawal, menopausal flushing, diabetic diarrhea, migraine prophylaxis
Transdermal patch delivering 0.2 mg/day clonidine applied every 7 days to hairless area of upper arm or chest.
Transdermal patch: 0.3 mg/day applied once every 7 days; initial dose 0.1 mg/day, titrate weekly by 0.1 mg/day increments to desired response.
Terminal elimination half-life: 12–16 hours (up to 48 hours following transdermal administration due to continued absorption from the skin depot).
Terminal elimination half-life is 12-16 hours after oral administration; with transdermal delivery, the effective half-life is prolonged to 20-40 hours due to continued absorption from the skin depot. In renal impairment, half-life may extend to 40 hours or longer.
Approximately 50% of clonidine is metabolized in the liver via cytochrome P450 (CYP) enzymes, primarily CYP2D6; the remainder is excreted unchanged in the urine.
Clonidine is extensively metabolized in the liver by cytochrome P450 enzymes (CYP2D6) to inactive metabolites; approximately 50% excreted unchanged in urine.
Renal: ~65% as unchanged drug; biliary/fecal: ~20% as metabolites; about 15% eliminated as metabolites in urine.
Approximately 40-60% of the absorbed dose is excreted unchanged in urine. About 20-30% is eliminated as metabolites via bile and feces. Renal clearance accounts for 50-60% of total clearance.
20–40% bound to plasma albumin.
Approximately 30-40% bound to albumin and alpha1-acid glycoprotein.
2.1 L/kg (moderate distribution into tissues, including brain and kidneys).
2.9-4.5 L/kg, indicating extensive distribution into tissues including the central nervous system.
Transdermal: approximately 60% of the drug released from the patch is absorbed systemically (compared to immediate-release oral bioavailability of 75–95%).
Transdermal system: Comparable to oral, approximately 50-80% of the dose reaches systemic circulation, with reduced peak-trough fluctuations. Oral: 70-80% (first-pass metabolism reduces bioavailability to ~40% in some individuals).
Cr Cl 10-30 m L/min: reduce dose by 25-50%; Cr Cl <10 m L/min: reduce dose by 50-75%.
For GFR 10-50 m L/min: reduce initial dose to 0.1 mg/day; for GFR <10 m L/min: use 0.1 mg/day and adjust cautiously, dosing interval may be extended to every 14 days; not dialyzable.
Severe hepatic impairment (Child-Pugh C): reduce dose by 50%.
No specific Child-Pugh based recommendations; use with caution in severe hepatic impairment due to possible accumulation; monitor for hypotension and bradycardia.
Not recommended for use in pediatric patients; safety and efficacy not established.
Safety and efficacy not established; use not recommended in pediatric patients.
Initiate at lowest dose (0.1 mg/day patch) due to increased sensitivity and risk of hypotension; titrate slowly based on BP response.
Initiate at 0.1 mg/day; titrate slowly due to increased sensitivity and risk of hypotension; monitor for dizziness, syncope, and renal function declines.
No FDA black box warning.
None
Rebound hypertension upon abrupt discontinuation (particularly at high doses or with beta-blocker combination),CNS depression (drowsiness, sedation),Bradycardia and heart block,Dry mouth, constipation, and orthostatic hypotension,Impaired renal function (dose adjustment required),Rash and contact dermatitis from transdermal patch
Rebound hypertension upon abrupt discontinuation (dose tapering required),CNS depression (sedation, dizziness),Bradycardia and heart block (use caution with conduction abnormalities),Orthostatic hypotension,Renal impairment (dose adjustment needed),Contraindicated in patients with severe bradycardia or sick sinus syndrome
Hypersensitivity to clonidine or any component of the patch,In patients with active bradycardia or sick sinus syndrome (without pacemaker),Concomitant use with other centrally acting alpha-2 agonists (e.g., methyldopa)
Hypersensitivity to clonidine or any component of the patch,History of severe bradycardia or sick sinus syndrome
Avoid alcohol and grapefruit juice; may increase drug effects.
No specific food interactions. Limit alcohol intake as it may potentiate hypotensive and sedative effects.
Clonidine (Catapres-TTS-2) is classified as FDA Pregnancy Category C. Animal studies have shown fetal harm at high doses. Human data are limited; however, use during pregnancy, especially in the first trimester, should be avoided unless clearly needed. A small increased risk of congenital malformations, particularly oral clefts, has been suggested in some retrospective studies, but not confirmed. Third-trimester use may cause maternal hypotension and reduced placental perfusion. Neonatal withdrawal (hypertension, irritability, tremor) may occur if used near term.
First trimester: No evidence of major congenital malformations in human studies; avoid use unless benefit outweighs risk. Second and third trimesters: Associated with decreased placental perfusion and fetal growth restriction; may cause fetal bradycardia, hypotension, and hypoxia. Discontinue or reduce dose if fetal distress occurs.
Clonidine is excreted into human breast milk with a milk-to-plasma ratio of approximately 1.5. Concentrations in milk are similar to maternal plasma levels. Use during breastfeeding is not recommended due to potential adverse effects in the infant, including hypotension, bradycardia, and sedation. If used, monitor infant for these effects.
Clonidine is excreted into breast milk; M/P ratio approximately 1.5:1. Limited data on infant effects; potential for infant hypotension, bradycardia, and sedation. Use with caution and monitor infant for adverse effects.
No specific dose adjustments are recommended for clonidine during pregnancy. However, increased plasma volume and enhanced renal clearance in pregnancy may reduce drug concentrations, potentially requiring dose titration to achieve blood pressure control. Close monitoring is warranted. The transdermal system (Catapres-TTS) may have variable absorption during pregnancy; consider switching to oral formulation if efficacy is compromised.
Increased plasma volume and renal clearance in pregnancy may require dose adjustment; empirical dose reduction in third trimester is not recommended; titrate to achieve optimal blood pressure control while avoiding maternal hypotension and fetal compromise.
Catapres-TTS-2 is a transdermal clonidine patch delivering 0.2 mg/day. Apply to hairless, intact skin on upper arm or chest; replace every 7 days. Avoid abrupt discontinuation to prevent rebound hypertension. Monitor for local skin reactions, bradycardia, and orthostatic hypotension. May cause dry mouth and drowsiness.
Catapres-TTS-3 (clonidine transdermal system) delivers 0.3 mg/day. Apply to hairless, intact skin on upper arm or torso. Rotate site weekly to minimize local irritation. Do not cut or trim patch. If patch falls off, replace with new patch. Onset of action delayed ~2-3 days after first application; oral clonidine may be needed initially. Contraindicated in patients with history of hypersensitivity to clonidine. Use cautiously in severe coronary insufficiency, recent MI, cerebrovascular disease, or chronic renal failure. Rebound hypertension may occur if patch is removed abruptly; taper over 2-4 days if discontinuing. May cause dry mouth, drowsiness, dizziness, constipation, and orthostatic hypotension.
Apply patch to clean, dry, hairless skin on upper arm or chest; do not cut or trim patch.,Replace patch every 7 days; remove old patch before applying new one at a different site.,Do not stop using patch suddenly; may cause dangerous rise in blood pressure.,May cause dry mouth, drowsiness, or dizziness; avoid driving if affected.,If patch falls off, apply a new one; if it becomes loose, cover with adhesive bandage.,Keep patches away from children and pets; used patches still contain active drug.
Apply patch once every 7 days to a clean, dry, hairless area of skin on the upper arm or torso.,Do not cut or trim the patch; use a new patch if it falls off.,Rotate application site weekly to prevent skin irritation.,Avoid applying patch to irritated or scarred skin.,Do not stop using the patch without talking to your doctor; abruptly stopping can cause a dangerous rise in blood pressure.,If you have surgery, inform your surgeon you are using this patch.,Side effects may include dry mouth, drowsiness, dizziness, and constipation. Avoid driving or hazardous activities until you know how the patch affects you.,Alcohol can increase drowsiness and dizziness; limit alcohol consumption.
No interactions on record
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about CATAPRES-TTS-2 vs CATAPRES-TTS-3, answered by our medical review team.
CATAPRES-TTS-2 is a Central Alpha-Agonist that works by Clonidine is a centrally acting alpha-2 adrenergic agonist that stimulates alpha-2 adrenergic receptors in the brainstem, activating inhibitory neurons and reducing sympathetic outflow from the central nervous system, resulting in decreased peripheral vascular resistance, heart rate, and blood pressure.. CATAPRES-TTS-3 is a Central Alpha-Agonist that works by Clonidine is an alpha-2 adrenergic agonist that reduces sympathetic outflow from the central nervous system, resulting in decreased peripheral vascular resistance, decreased heart rate, and lowered blood pressure.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between CATAPRES-TTS-2 and CATAPRES-TTS-3 depend on the specific clinical indication. These are both Central Alpha-Agonist agents and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of CATAPRES-TTS-2 is: Transdermal patch delivering 0.2 mg/day clonidine applied every 7 days to hairless area of upper arm or chest.. The standard adult dose of CATAPRES-TTS-3 is: Transdermal patch: 0.3 mg/day applied once every 7 days; initial dose 0.1 mg/day, titrate weekly by 0.1 mg/day increments to desired response.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between CATAPRES-TTS-2 and CATAPRES-TTS-3 in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. CATAPRES-TTS-2 is classified as Category C. Clonidine (Catapres-TTS-2) is classified as FDA Pregnancy Category C. Animal studies have shown fetal harm at high doses. Human data are limited; however, use during pregnancy, esp. CATAPRES-TTS-3 is classified as Category C. First trimester: No evidence of major congenital malformations in human studies; avoid use unless benefit outweighs risk. Second and third trimesters: Associated with decreased pla. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.