- See: Transdermal 
* For HTN, opioid & tobacco withdrawl;

- Central alpha adrenergic receptor agonist; 
* Adult: 0.05-0.10 mg PO bid-qid adjusted daily by 0.1-0.2 mg increments 
- initial oral doses of 0.1 mg are given twice daily and adjusted to usual maintenance dose of 0.2 to 0.8 mg/day; 
- maximum recommended oral doses are 2.4 mg/day; 
- See Transdermal Patch; 
- HTN Emergency: 0.1-0.2 mg PO then 0.1 mg q1 hr upto 0.8 mg - Precautions: 
* Note that must taper when d/c'ing or will get rebound hypertension;

- if discontinued abruptly, severe hypertension may occur, therefore, drug should be tapered; 
* Max dose 2.4 mg/day; 
* more effective for HTN when combined with diuretic; 
* Note side effects dry mouth, drowsiness, sedation occur frequently; 
* severe renal insufficiency requires a reduced dose; 
- PHARMACOKINETICS: 
- onset of Antihypertensive activity is 30 to 60 minutes after PO or IV dosing; 
- peak antihypertensive activity occurs within 2 to 4 h; 
- duration of Antihypertensive effect is 6 to 10 h; 
- oral bioavailability ranges from 65% to 96%; 
- elimination half-life is 6 to 23 h; 
- hepatic metabolism to inactive metabolites is followed by renal and fecal excretion of unchanged compound (65% and 22%, respectively). 
- DOSAGE IN RENAL FAILURE 
- patients with severe renal failure (GFR < 10 mL/minute) should receive 50% of usual dose of clonidine given at the normal dosage interval