First-Pass Effect

What is first pass metabolism?
This occurs when drug molecules in the stomach and intestines are diverted into the hepatic portal circulation before they have a chance to enter the systemic circulation.

Because the liver is the primary organ of metabolism, the consequence of first-pass metabolism is the break down of significant amounts of a drug before it can reach the systemic circulation, so those drugs never reach the site of action!

Considering that the first pass metabolism involves drug molecules in the stomach and intestines, what routes of administration would this concern?
This affects primarily drugs given by mouth or enteral feedings. It will occur to a lesser amount by drugs administered rectally

What is done to compensate for first pass effect?
While giving medication by other routes would eliminate this problem, it is often more costly and less convenient. Instead, drugs given by mouth are usually given in higher doses. Sometimes these are much higher doses than would be given IV.

Bioavailability is the percentage of drug administered that is absorbed. (Remember that absorption is the drug’s journey from the site of administration to the SYSTEMIC circulation, not hepatic portal circulation).
How will first pass metabolism affect bioavailability?
Because much of the drug will be metabolized (broken down) before it gets a chance to enter the systemic circulation, bioavailability will be decreased.

aka Biodisposition; The effects of biologic systems on drugs. It deals w/ the Absorption, Distribution, & Elimination of Drugs. Loading & Maintenance Doses can be calculated. What is Pharmacokinetics? What processes are involved? What can be calculated in Pharmacokinetics? The …

Absorption refers to the movement of drug into the bloodstream, with the rate dependent on the physical characteristics of the drug and its formation. Refers to the passage of drug molecules from the site of administration into the circulation. Active …

Name the six routes of drug administration topical oral parenteral rectal inhalation transdermal Topical for skin or mucous membranes – local reaction cream, ointment, eye, ear or nose drops WE WILL WRITE A CUSTOM ESSAY SAMPLE ON ANY TOPIC SPECIFICALLY …

Onset of action? the time it takes a drug to reach the concentration necessary to produce a therapeutic effect Peak effect is the maximum drug effect produced by a drug once the drug has reached its maximum concentration in body …

The manner a drug enters the body is referred to as the route of administration. There are many different routes than can be utilized. The routes are: orally, otically, nasally, transdermal, rectally, vaginally; or injected through the skin in several …

Absorption Absorption describes the transfer of drug from the site of administration to the general circulation The aim of drug therapy is to rapidly deliver & maintain therapeutic, yet nontoxic levels of drug in the target tissues. WE WILL WRITE …

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