IHD treatment Flashcards
principles of IHD treatment
reduce afterload and preload to reduce O2 consumption (DD) and/or vasodilation to increase blood supply (SS)
Classes of drugs for IHD treatment
- Nitrates
- Ca channel blockers
- B blockers
- Antiplatelet drugs
- statins
Nitrates moa
smooth muscle relaxation: NO activates guanylyl cyalse –> convert GTP to cGMP –> dephosphorylation of MLC
- DD: reduces O2 consumption due to
a. venodilation (reduce preload)
b. arteriolar dilation (reduce afterload) - SS: increase coronary blood flow or redistributes coronary flow from normal to ischemic regions
Nitrates PK
sublingual:
- 1-5min onset, 10-30 mins doa
transdermal:
- 30-60min onset, 7-10hrs doa
Activity of different nitrates
Highest activity: glyceryl trinitrate/nitroglycerin (has 3 NO2 groups)
Significant activity: glyceryl dinitrate
Lower activity: glyceryl mononitrate
Nitrates clinical uses
- IHD
2. Hypertension
Nitrates adverse effects
adverse effects due to vasodilation
- tachycardia: reduced BP –> baroreflex –> stimulate CV center in medulla oblongata (but reflex does not last long)
- hypotension
- headache - meningeal artery vasodilation –> increased intracranial pressure
Tolerance to nitrates
GSH S-transferase can convert trinitrate to mononitrate
need to increase dose for prolonged use
Effect of nitrates alone on:
- HR
- Arterial pressure
- End diastolic pressure and fiber tension
- Contractility
- Ejection time
- HR reflex increase
- arterial pressure decrease
- end diastolic pressure decrease
- contractility reflex increase
- ejection time reflex decrease
Effect of nitrates when used together with B blockers/Ca channel blockers:
- HR
- Arterial pressure
- End diastolic pressure and fiber tension
- Contractility
- Ejection time
- HR decrease
- Arterial pressure decrease
- End diastolic pressure no change/decrease
- Contractility no change
- Ejection time no change
B blockers MOA for IHD
reduce contractility of heart –> reduce O2 consumption
Ca channel blockers MOA for IHD
DD:
- reduce O2 consumption by
1. smooth muscle relaxation - vasodilation reduce afterload and preload
2. reduce contractility
3. reduce BP
SS:
- increase blood supply by
1. smooth muscle relaxation - vasodilation
Name 2 non DHP Ca channel blockers
verapamil, diltiazem
DHP and non DHP Ca channel blockers differences
General:
- DHP better at vasodilation
- non DHP better at cardiac depression
Hypertension: verapamil = diltiazem = nefepine
Vasodilator: nifedipine > diltiazem > verapamil
Cardiac depressant: verapamil > diltiazem > nifedipine