DESCRIPTION
Moxonidine is a new-generation centrally acting antihypertensive drug approved for the treatment of mild to moderate essential hypertension. It may have a role when thiazides, beta-blockers, ACE inhibitors and calcium channel blockers are not appropriate or have failed to control blood pressure. In addition, it demonstrates favourable effects on parameters of the insulin resistance syndrome, apparently independent of blood pressure reduction.
CATEGORIES
Alpha2 Agonists Antiadrenergic Agents, Centrally Acting Antihypertensive Agents Cardiovascular Agents Cardiovascular System Hypotensive Agents Imidazoline Receptor Agonists Sympatholytics
CHEMICAL FORMULA
C9H12ClN5O
COMPOSITION
Moxonidine 0.2 MG
INDICATION
For the treatment of mild to moderate essential or primary hypertension . Effective as most first-line antihypertensives when used as monotherapy .
PHARMACODYNAMICS
Antihypertensive agent whose site of action is the Central Nervous System (CNS), specifically involving interactions with I1- imidazoline and alpha-2-adrenergic rececptors within the rostral ventrolateral medulla (RSV).
MECHANISM
Stimulation of central alpha 2-adrenergic receptors is associated with sympathoadrenal suppression and subsequent reduction of blood pressure. As this class was further explored it was discovered that sympathoadrenal activity can also be suppressed by a second pathway with a newly discovered drug target specific to imidazolines. [5] Specifically, moxonidine binds the imidazoline receptor subtype 1 (I1) and to a lesser extent alpha-2-adrenoreceptors in the RSV causing a reduction of sympathetic activity, reducing systemic vascular resistance and thus arterial blood pressure.
ABSORPTION
90% of an oral dose is absorbed with negligible interference from food intake or first pass metabolism, resulting in a high bioavailability of 88%.
METABOLISM
Biotransformation is unimportant [3] with 10-20% of moxonidine undergoing oxidation reactions to the primary 4,5-dehydromoxonidine metabolite and a guanidine derivative by opening of the imidazoline ring.
ELIMINATION
Elimination is nearly entirely via the kidneys with a majority (50 -75%) of overall moxonidine being eliminated unchanged through renal excretion. Ultimately, more than 90% of a dose is eliminated by way of the kidneys within the first 24 hours after administration, with only approximately 1% being eliminiated via faeces.
HALF LIFE
Plasma elimination half life is 2.2 – 2.3 hours while renal elimination half life is 2.6-2.8 hours.
TOXICITY
Contraindicated due to known hypersensitivity to an ingredient (Physiotens tablets contain lactose), heart failure, severe renal impairment, < 16 years old, >75 years old, bradycardia, severe bradyarrhythmia, sick sinus syndrome, second or third degree atrioventricular block, malignant arrhythmias.