Ever wondered why some drugs are not given orally even though swallowing a tablet is easier?
When a drug is taken by mouth, it first travels to the liver through the portal circulation before reaching systemic circulation. This process is called First-Pass Metabolism — where a significant portion of the drug gets metabolized before it can exert its therapeutic effect.
Why does it matter?
• Reduces drug bioavailability
• Alters required dose strength
• Influences route of administration
• Can lead to variability in patient response
Clinical Insight:
Drugs with extensive first-pass metabolism (like nitroglycerin or propranolol) are often given via sublingual, transdermal, or intravenous routes to bypass the liver initially.
Understanding first-pass metabolism helps pharmacists and healthcare professionals design safer and more effective drug therapies.
MBH/PS