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Thursday, March 22, 2007

cGMP is High Yield

  • Know that the drugs acting via cGMP are
    • Nitrates (Nitroglycerin, isosorbide dinitrate)
      • Increases production of cGMP
        • Activation (denitration) to NO occurs within the smooth muscle cells enwrapped around vascular endothelium.
          • NO activates guanylyl cyclase↑cGMP → dephosphorylates myosin light chain kinase → smooth muscle relaxation
      • Note, tolerance develops rapidly
        • Addressed by telling pt to take a break from the particular drug or Rx w/ a different anginal drug
      • Occupation exposure → Monday Disease
    • Nitroprusside
      • Rx: Hypertensive emergencies
      • Same mechanism as nitrates
      • AE: Cyanide toxicity (rx: sodium thiosulfate)
    • Sildenafil
      • Decreased breakdown of cGMP
        • Inhibits 5’-phosphodiesterase
          • The enzyme that breaksdown cGMP
    • Do not give a pt on a nitrate sildenafil (will synergistically cause their diastolic BP to fall through the floor!)
      • Instead give Alprostadil
      • If you accidentally did combine the 2 above what drug would you want to give?
        • α-1 agonist
    • Hydralazine
      • dilates arterioles more than veins= reduces afterload; AE: SLE like syndrome
  • Know that ANP (Atrial Natriuretic Peptide) acts by activating guanylyl cyclase


ayezaw said...

Hydralazine= arteriolar dilator
Nitroprusside=arteriolar and venular dilator

Anonymous said...

Isn't hydralazine an arterial dilator; not a venodilator...

Mike said...

apologize for the error. yes, Nitroprusside is an arteriolar dilator. Remember the arterioles are the area where BP is regulated the most.