Active metabolite of alpha methyldopa. Acts on the central alpha 2 adrenergic receptors to decrease central sympathetic outflow. Precursor form – alpha methyldopa – is used as an antihypertensive.

Diuretics eg: hydrachlorothiazide
Angiotensin converting enzyme inhibitors  eg: enalapril, ramipril
Angiotensin receptor blockers eg:losartan, candesartan
Adrenergic blocking agents eg: propranalol, atenelol
Calcium Channel blockers eg: verapamil, diltiazem
Central sympatholytics eg: clonidine
Vasodilators eg: hydralazine

Clonidine
Clonidine is an imidazoline derivative and is a Alpha 2 adrenergic agonist, particularly alpha 2a. The hemodynamic effects are due to activation of Alpha 2 (especially alpha 2a) receptors located postjunctionally in the vasomotor centre. This causes decreased central sympathetic outflow which results in bradycardia and fall in BP (also due to increased vagal tone). The plasma NA level decreases.  Clonidine is a moderately effective antihypertensive.
It was used as an antihypertensive in the 60′s and 70′s. But due to frequent side effects, it is now rarely used. The other indications …

Alpha-2 adrenergic receptor – Location, Actions, Agonist, Antagonists
Location:

Prejunctional – adrenergic nerve endings
Post junctional – brain, pancreatic B cells
Extrajunctional – certain blood vessels, platelets

Actions:

Inbition of neurotransmitter release
Decreased central sympathetic outflow
Decreased insulin synthesis
Vasoconstriction
Platelet aggregation

Agonist – Clonidine
Antagonist – Yohimbine, Rauwolscine

Drugs which decrease the level of circulating lipids and lipoproteins. They help reduce risk of cardiovascular disease by retarding the formation of atherosclerotic plaques.

Intravenous magnesium sulphate. Intravenous magnesium sulphate is also useful in the treatment of refractory hypokalemia, often associated with hypomagnesemia and also for the treatment of torsades de pointes.

IV – 2-5 minutes
IM – 10-10 minutes
Oral – 20-40 minutes

Duration of action – 3-6 hours

Better diuresis
Less hypokalemia at equinatriuretic doses
Less hyperuricemia
Less hyperglycemia

It is a loop diuretic.
Mechanism of action

secreted into the renal tubule by the organic anion transporter in the proximal tubule
inhibits the Na+ K+ 2Cl- co-transporter in the thick ascending limb of loop of Henle by binding to Cl- binding site
increases local prostaglandin synthesis
weak carbonic anhydrase inhibitor

Actions in renal tubule:

abolish corticomedullary osmotic gradient
block positive and negative free water clearance (urine becomes isosmotic with plasma)
increases bicarbonate excretion and urine pH by inhibiting carbonic anhydrase
increases excretion of K+ (by increasing Na+ reaching the distal tubule)
increases excretion of Ca2+, Mg2+
decreases excretion of uric acid …

PG – Acronym, abbreviation
Prostaglandin