First pass metabolism can be defined as metabolism of a drug molecule which occurs during passing through the gut wall and then in liver before a drug molecule goes in to systemic circulation.
That is a metabolism of a drug occurring while a drug is being absorbed from stomach and intestine and then the metabolism of drug occurring in liver after it is absorbed and going before the systemic circulation.
When a drug is administered through oral route it is absorbed from digestive tract and while it is being absorbed , it comes in contact with many enzymes like esterase , and oxidase, and deaminase and so on , which are capable of metabolizing a drug molecule in to an inactive form .
Thus many times the active drug molecules reaching in systemic circulation is very little.
Liver is the main organ in body which is responsible for protecting our body from any of incoming foreign material in to body, be it a drug molecule, or a microorganism or a particulate matter or foreign protein molecule.
Microphages present in liver are capable of imbibing a bacterium within fraction of a minute and then dissolves and digests bacteria or microorganism. Cytochrom p450 enzyme system which is a part of livers metabolic system is mainly responsible for metabolism of organic substances entering in the liver. After a drug is metabolized in to an inactive form it is excretion in to bile , bile is excreted in to intestine , some drugs get reabsorbed from this point from intestine owing to their solubility, a highly fat soluble molecule is more likely to get reabsorbed in to intestine.
A drug molecule in liver is subjected to various metabolic enzymes; some times a drug may be transformed in to an active form in liver, the phenomenon is known as biotransformation, then from liver the drug enters in to systemic circulation.
First pass metabolism can be bypassed or avoided if a drug is administered through Intravenous, intramuscular, subcutaneous, sublingual, rectal, routes of administration, as the drug molecule directly enters in to systemic circulation, from the site of application.
What are the factors affecting absorption of drug:
1.Route of admistration of a drug
2.Drug molecule :
This is one of the main factor which affect the absorption of drug from site of administration, in all routes of administration of drug other than paranteral route
* Polarity of molecule.
*.Pka of drug molecule
*.Persons disease conditions
*.Food taken along with drug or food present in gut.
*.Drug interactions of concomitantly administered other drugs
Do you know now this website has become a most popular and most referred website in pharmaceutical industry and pharmaceutical companies all over the world ,for almost all topics related to Pharmaceutical Manufacturing , Pharmaceutical Regulatory Affairs and Good Manufacturing Practice and latest news and new drugs developments.
What is What is 510(k) Clearances ?
What is 510(k) Clearances,
Premarket Notification for medical devices – PMN or 510(k)
Antibiotic Definition and classification
Antibiotic resitance and Antibiotic resistance mechanism
Vitamin D Details on FDA cautions on accurate dosage of Vitamin D
What is an antibody? what is monoclonal and polyclonal antibodies?
Enzyme linked immunosorbent assay ELISA
Pharmaceutical Aseptic Manufacturing Process Terms , Terminology and Definitions.
Here are some articles which will be useful for you in further understanding of aspects of sterile dosage form manufacturing and regulatory affairs and good manufacturing practice in
Types of validations in pharmaceutical manufacturing
Requirements of documents for validation of sterilisation process
How to investigate OOS out of specification results
Determination of Phenol coefficient of a disinfectant
Time limitations in sterile pharmaceuticals processing
Aspects of validation of manufacturing process in sterile pharmaceuticals
Controlling Pyrogens in injectable dosage forms
Media fill run process simulation aspects Validation of Aseptic Process and Sterilisation
New Drug Application (NDA) how to make a New Drug Application (NDA) to US FDA
Abbreviated New Drug Application (ANDA) What is ANDA , detaied information about ANDA preparation and submission to US FDA
How to make Investigational New Drug (IND) Application to US FDA
Drug applications submission to us fda Over the counter Drugs OTC drugs
BIOAVAILABILITY AND BIOEQUIVALENCE REQUIREMENTS
Electronic record in pharmaceutical manufacturing industry
Good manufacturing practice in pharmaceutical industry
Pharmaceutical industry pharmaceutical companies and FDA latest updates
Here is an interesting article on world wide pharmaceutical industry
Article on Pharmaceutical Industry pharmaceutical industry
Here are some interesting articles on Quality assurance systems for pharmaceutical company
1.Quality assurance in pharma industry
2.Quality by designe concept for pharmaceutical industry
3.Quality by designe concept in pharmaceutical industryan explanation