Cardiac- Vasodilators

Question 1

Nitroglycerin MOA

Answer 1

Forms free radical nitric oxide in turn causing smooth muscle relaxation. Venous>arteriole. Primarily reduces cardiac oxygen demand by decreasing preload (left ventricular end- diastolic pressure); may modestly reduce afterload; dilates coronary arteries and improves collateral flow to ischemic regions

Question 2

Nitroglycerin contraindications, cautions and adverse effects

Answer 2

Hypersensitivity, concurrent use of PDE-5 inhibitors (viagra, levitra, cialis), acute circulatory failure/shock, increased ICP, severe anemia

Avoid in SBP <90 or >30 below baseline,
30>HR>100, and/or suspected RVI

Adverse reactions:
Headache, hypotension
*tachyphylaxis develops within 24-48hrs of continuous infusion

Question 3

Nitroglycerin indications and dosages

Answer 3

Lower doses cause venodilation, higher cause arterodilation

Continuous infusions:
ADHF 5-10mcg/min, titrate by 5-10mcg/min q 3-5min up to 200mcg/min

Angina- (initial) 5-10mcg min, titrate by 5mcg/min q 5-10min up to 20mcg/min. If angina persists, increase by 10-20mcg/min q 3-5min up to 400mcg/min (200mcg/min soft max. per VPP)

Topical patch, transdermal: Initial: 0.2 to 0.4 mg/hour; increase dose as needed based on response and tolerability to a maximum of 0.8 mg/hour. Use a patch-on period of 12 to 14 hours/day and patch-off period (nitrate-free interval) of 10 to 12 hours/day to minimize the risk of tolerance.

Hypertensive crisis (adjunct, off label)
Variable efficacy compared to other agents (eg, inconsistent and transient BP response), possible reflex tachycardia, and possible reduced cardiac output. Goal of therapy is to reduce MAP by ~10% to 20% over the first hour, then by an additional 5% to 15% over the next 23 hours

Continuous IV infusion: Initial: 5 mcg/minute; increase based on BP response and tolerability in increments of 5 mcg/minute every 3 to 5 minutes up to 20 mcg/minute; if no response at a dose of 20 mcg/minute, may increase by 10 to 20 mcg/minute every 3 to 5 minutes to a maximum dose of 200 mcg/minute.

Question 4

Nitroglycerin infusion prep

Answer 4

50mg/250mL (NS or D5W)= 200mcg/mL

Question 5

Nitroglycerin Pharmacokinetics

Answer 5

Onset: IV immediate, SL 1-3min, transdermal ~30min

Duration: IV 3-5min, SL >25 min, transdermal 10-12hrs