Page 172 - pharma 1 theoretical updated MNU_Neat

Clinical pharmacy 2024/2025 Level 3 Pharm D Pharmacology 1 (PO 502)
 Aspirin must be avoided (7-14 days) before surgical operation why?

 To avoid increased blood loss if taken before surgery.
 NSAIDs e.g., Ibuprofen, if taken concomitantly with, or 2 hours prior to aspirin,
can obstruct the access of aspirin to the serine residue of COX 1 → antagonize the

platelet inhibition by aspirin.
 Therefore, aspirin should be taken at least 30 minutes before other NSAIDs as
ibuprofen or at least 8 hours after ibuprofen.
 COX-2 inhibitors (Coxibs e.g., celecoxib) do not have antiplatelet effects and may

contribute to cardiovascular events by shifting the balance of chemical mediators
in favor of thromboxane A2.
 i.e., patients taking coxibs still need low-dose aspirin for cardiovascular

protection.

2- (PDE-3) Inhibitors

Dipyridamole

 Pyridopyrimidine derivative ➔ has antiplatelet and vasodilatory properties.

 Mechanism

➢ Inhibits PDE-3 responsible for degradation of cAMP to AMP in platelets (and

blood vessels) → increasing cellular concentrations.
➢ It inhibits adenosine reuptake → increased extracellular adenosine
concentrations and hence the activity of adenosine at A1 and A2 receptors on
platelets → increases cAMP levels → decreased platelet aggregation.

➢ Stimulate PGI release and inhibits TXA formation.
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