Vasodilators Lecture 5 Flashcards
Descrive the 2 types of vasodilator drugs
Indirect and direct
INdirectL drugs which block vasoconstriction (ANS, RASS)
Direct : working on the machinary within the cell to cause vasodilation
Describe calcium channel blockers as vasodilators to alter ABP
Stop influx of calcium to the smooth muscle cell of the vessel and initiating contraction
Dihydropyridine (DHPs) eg. Nifidipine, nimodipine L-type channel blockers
Used in angina for coronary vessel walls and systemic vessels (more constriction in veins)
Peripheral vascular disease- Raynaud’s sydrome- extreme basic instruction in extremities
May have use for improved cerebral function after a stroke or in dementia
Side effects- flushing (red face) and decreased GIT activity
Describe K channel acivators as vasodilators
Open K channels to allow K efflux and causing the hyperpolarisation of the cell Eg. Minoxidil, cromakalim
Work by ATP-modukated K channels (K(ATP)) causing efflux and hyperpolarisation and decrease Ca2+ entry.
Primarily arterial effects to reduce total peripheral resistance
Used in severe hypertension only as there are more side effects- headache/flushing, tachycardia, oedema
Describe organic nitrates as vasodilators
Eg glyceryl trinitrate (GTN)
Work by releasing NO to upregulate guanylyl cyclase and increase GMP, which inhibits K+ channels and myosin/actin
Used in angina, coronary vessels and systemic circulation (more constriction in arterioles)
Side effects- excess vasodilation- hypotension, refelkx tachycardia, headache
Administered sublingually or transdermally for prophylaxis
Other egs. Isosorbide mono/dinitrate Amyl nitrate (Poppers)- tolerance
Sodium nitroprusside- NO release to increase cA/GMP- used in hypertensive emergencies
Describe PDE inhibitors as vasodilators
Phospohodiesterases
Example: Viagra
Mechanism:
-Inhibition increases levels of cGMP and/or cAMP depending on which PDE inhibited
PDE type 5- sildenafil (Viagra) used in impotence- erection
