Clonidine is an alpha 2-adrenergic agonist used in the treatment of attention-deficit/hyperactivity disorder (ADHD).

Pharmacokinetics of Clonidine

Absorption Clonidine is rapidly absorbed, with 100% bioavailability when given by mouth (Tmax = 3 to 5 hours)
Distribution Clonidine is highly lipid soluble and distributes throughout the body. Clonidine is primarily to bound to albumin.
Metabolism 50% hepatically, but does not seem to interact with other drugs via CYP450 system
Elimination 50% is excreted unchanged by the kidneys
Half-life 5 to 13 hours

Clonidine: Cytochrome P450 Metabolism

Substrate of (Metabolized by)
  • Clonidine binds to all three alpha 2-adrenergic receptor subtypes (2A, 2B, 2C) and other receptors (a1- and beta- adrenergic, histamine, imidazoline)

Dosing for Clonidine

Starting ADHD: 0.025 mg BID or 0.05 mg daily
Titration ADHD: Increase every 3-7 days by 0.05 mg/day
Maximum ADHD: Maximum 0.4 mg (children)
Taper Slowly taper dose over several weeks to avoid withdrawal symptoms and rebound hypertension
  • Multiple daily doses is recommended in the treatment of ADHD (QID dosing is often ideal, but TID or even BID dosing may do – especially if adherence is a concern).
  • More frequent dosing is preferred because of clonidine's short half-life, and because a greater number of smaller doses may be less sedating than a smaller number of bigger doses.
  • Clonidine comes in oral and transdermal patches