Moxilong

Indications

• Mild to moderate essential hypertension

Dosage

Children: Refer to the BNF for Children for specific dosing information.

Adults: 200 micrograms once daily for 3 weeks, then increased if necessary to 400 micrograms daily in 1-2 divided doses (max. 400 micrograms per day).

Mechanism of action

Moxonidine stimulates central alpha-2-adrenergic receptors and binds specifically to imidazoline receptor subtype 1 (I1), leading to sympathoadrenal suppression. This results in reduced sympathetic activity, decreased systemic vascular resistance, and ultimately lowers blood pressure. Moxonidine has a lower affinity for central alpha-2-adrenergic receptors, which helps reduce the incidence of sedation and dry mouth, common side effects of other centrally acting antihypertensives.

Pharmacodynamics

Moxonidine is an antihypertensive agent that operates within the central nervous system, particularly affecting the rostral ventrolateral medulla. Its primary interaction with I1-imidazoline receptors and alpha-2-adrenergic receptors results in a decrease in sympathetic outflow, effectively lowering blood pressure without the sedation typically associated with other medications in its class.

Pharmacokinetics

Moxonidine is absorbed rapidly after oral administration, reaching peak plasma concentrations within 1 to 2 hours. It undergoes extensive hepatic metabolism, primarily through the liver, and has a half-life of approximately 2-4 hours. The drug is mainly excreted through urine, with renal function influencing its clearance. Dosage adjustment may be necessary in individuals with renal impairment.

Contra-indications

• Bradycardia
• Second- or third-degree AV block
• Severe heart failure
• Sick sinus syndrome
• Sino-atrial block

Adverse effects

• Drowsiness
• Dry mouth
• Hypotension
• Fatigue
• Nausea
• Headaches

Interactions

• Alcohol may enhance sedative effects
• May interact with other antihypertensives
• Caution with beta-blockers due to potential additive effects

Precautions

• Monitor blood counts and liver function before treatment and at intervals during the first 6-12 weeks
• Use with caution in the elderly
• May impair the ability to perform skilled tasks such as driving

Pregnancy

Moxonidine should be used in pregnancy only if the potential benefit justifies the potential risk to the fetus. Consult healthcare professionals for guidance.

Breast-feeding

It is unknown whether moxonidine is excreted in human breast milk. Caution is advised when administering to breastfeeding mothers.

Storage

Store at room temperature, away from moisture and heat.

Formulations

• Moxonidine 200 microgram tablets
• Moxonidine 300 microgram tablets
• Moxonidine 400 microgram tablets

Mechanism of action

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. Specifically, moxonidine binds the imidazoline receptor subtype 1 (I1) and to a lesser extent αlpha-2-adrenoreceptors in the RSV causing a reduction of sympathetic activity, reducing systemic vascular resistance and thus arterial blood pressure. Moreover, since alpha-2-adrenergic receptors are considered the primary molecular target that facilitates the most common side effects of sedation and dry mouth that are elicited by most centrally acting antihypertensives, moxonidine differs from these other centrally acting antihypertensives by demonstrating only low affinity for central alpha-2-adrenoceptors compared to the aforementioned I1-imidazoline receptors.

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).