Where does the first-pass metabolism of the drug occur?
liver
The first-pass effect can occur in the gastrointestinal tract, the liver and lung. Although the liver is the main drug metabolizing organ in the body, the gut wall can play an important role in the first-pass metabolism of certain drugs.
How is ethinyl estradiol metabolized?
Metabolism: Steroidal estrogens, including estradiol, are metabolized primarily in the liver, where they are conjugated with sulfate and glucuronide. Because of the rapid metabolism, nonesterified forms of estrogen, including estradiol, must usually be administered daily.
What is first-pass metabolism in pharmacology?
The first pass effect (also known as first-pass metabolism or presystemic metabolism) is a phenomenon of drug metabolism whereby the concentration of a drug, specifically when administered orally, is greatly reduced before it reaches the systemic circulation.
Which route has highest first-pass metabolism?
Intravenous (IV) Injection straight into the systemic circulation is the most common parenteral route. It is the fastest and most certain and controlled way. It bypasses absorption barriers and first-pass metabolism.
What happens after first pass metabolism?
The first-pass metabolism or the first-pass effect or presystemic metabolism is the phenomenon which occurs whenever the drug is administered orally, enters the liver, and suffers extensive biotransformation to such an extent that the bioavailability is drastically reduced, thus showing subtherapeutic action (Chordiya …
What is first pass metabolism with example?
First pass metabolism can occur in the gut and the liver. For example, first pass metabolism occurs in the gut for benzylpenicillin and insulin and in the liver for propranolol, lignocane, chloromethiasole and GTN.
How long does ethinyl estradiol stay in your system?
EE is a long-acting estrogen, with a nuclear retention of about 24 hours.
What does ethinyl estradiol do to a womans body?
It works mainly by preventing the release of an egg (ovulation) during your menstrual cycle. It also makes vaginal fluid thicker to help prevent sperm from reaching an egg (fertilization) and changes the lining of the uterus (womb) to prevent attachment of a fertilized egg.
What is first pass effect with example?
Drug: Propranolol- ~26% Bioavailability because 75-85 % is metabolized by the liver before it can reach the circulation when taken orally. Drug: Morphine-~30% Bioavailability because 70% is metabolized via 1st pass effect if taken orally.
Can first-pass metabolism effect bioavailability?
Does 1st pass metabolism increase with age?
Ageing is associated with a reduction in first-pass metabolism. This is probably due to a reduction in liver mass and blood flow [52]. As a result, the bioavailability of drugs undergoing extensive first-pass metabolism such as propranolol and labetalol can be significantly increased [53–55].