Phosphodiesterase Inhibitors

Question 1

Milrinone

Answer 1

• Selective phosphodiesterase inhibitor (PDE III)
• inotropic
• vasodilator

Uses;

• tx of acute decompensated HF
• weaning pt off CPB
• management of acute. LV dysfunction after cardiac surgery
• congestive heart failure

MOA;
selective phosphodiesterase inhibitor (PDE III); blocks the breakdown of cAMP in the myocardium and vascular smooth muscle -increasing intracellular calcium in the heart causes increased contractility (inotropic effects)
-decreased intracellular calcium in the smooth muscle causes vasodilation and decreased PVR
-overall improves CO

Dose;

• IV; 50 mcg/kg
• infusion 0.5 mcg/kg/min

Pharmacokinetics;

• onset; 5 -15 min
• peak; 5 min
• E1/2t; 2.5 hours (severe CHF have longer half life)
• Vd; 0.3 -0.45 L/kg
• Pb; 70%

-80% excreted unchanged in the urine (decrease dose in renal failure)

Side Effects;
-very well tolerated; few side effects 
Small population experienced 
-hypotension
-angina
-headache 

Contraindicated;
-hypersensitivity

Caution;
renal dysfunction (decrease dose)