Learn what is pharmacokinetics and membrane transportation mechanisms in pharmacy. It is the study of how drugs move through our body.
How to define pharmacokinetics?
It is defined as the study of drug movement across body.
The word pharmacokinetics derived from two Greek word, Pharmakon (drugs) and kinesis (movement).
Drug concentration and site of action is depending on pharmacokinetics mechanism.
Few important aspects of pharmacokinetics are, Routes of Drug Administration, dose of drug, time needs for action, duration of action and frequency of drug administration.
Pharmacokinetics process includes transport mechanism of drug across biological membrane.
What is biological membrane?
This is a double layer membrane made up of Phospholipid, cholesterol molecules and proteins. Extrinsic and Intrinsic proteins are absorbed on lipid layer.
Protein can freely pass through the membrane. Lipid molecules also can show movement through biological membranes. This transportation mechanism of molecules (proteins, lipid) is Membrane transportation.
What is membrane transportation?
It is a mechanism, by which solute like ions, small molecules pass through biological membranes.
Drug transported across the membrane continued by following these two processes – passive transportation and active transportation.
What is Passive transportation?
When the drug passes across the cell membrane by follow concentration gradient known as passive transportation.
In this transportation mechanism metabolic energy does not require and membrane do not play any active role.
Here the concentration gradient act as a source of energy for transportation.
Passive transportation has 4 mechanisms – passive diffusion, facilitated diffusion, filtration and osmosis.
What is passive diffusion?
The transportation of high concentrated materials to lower concentration is known as passive diffusion.
What is facilitated diffusion?
When the drug molecules cross cell membrane via special transporter proteins in cell membrane, called facilitated diffusion. These special transporter proteins known as carrier protein.
What is Filtration?
When water and solute molecules move through membrane pores due to the cardiovascular system’s hydrostatic pressure. Lipid insoluble drugs can cross the membrane by filtration mechanism.
What is osmosis?
When the liquids watery molecules cross a selective permeable membrane called osmosis transport mechanism.
Osmosis follows the order of concentration of solution (Isotonic, hypertonic and hypotonic)
What is active transportation in pharmacokinetics?
When the molecules move across the cell membrane with the help of energy from lower concentration region to higher concentration region known as active transportation mechanism.
Active transportation required metabolic energy to move against the concentration gradient.
Active transportation can be two types, primary active transportation and secondary active transportation.
What is primary active transportation?
When the molecules moved into cell by hydrolysis of ATP, known as primary active transportation. Example, Sodium potassium pump (enzyme dependent).
What is secondary active transportation?
When the ions or molecules are transport across cell membrane by the help of energy generated from pumping of protons mostly Na+. Two main aspects of Secondary active transportation are – symport and antiport.
What is symport in pharmacy?
When ions or molecules and solutes are moves in same direction.
What is Antiport in pharmacy?
When ions or molecules and solutes are moves in opposite direction.
Also read Pharmacodynamics: Principle of Drug Action in Pharmacology.
Why membrane transportation is important for pharmacokinetics?
Membrane transportation is vital in pharmacokinetics for several reasons, such as drug absorption, distribution, metabolism and excretion.
Drug absorption
Membrane transport processes helps to determine how drugs are absorbed into the bloodstream from their site of administration. These processes help to predict the rate and extent of drug absorption.
Distribution
Once the drug is absorbed into the bloodstream then drugs are transported to various tissues and organs throughout the body. Membrane transport processes maintain the drug distribution by determining how drugs cross cellular barriers.
Metabolism
Maximum drugs undergo metabolism in the liver to form metabolites. Membrane transporters in hepatocytes (liver) help to take drugs from the bloodstream and their subsequent metabolism by hepatic enzymes.
Excretion
After metabolism drugs and their metabolites are eliminated from the body through excretion via the kidneys (renal excretion), bile (biliary excretion) or other routes.
Membrane transporters in renal tubules and hepatocytes play an important role in drug excretion. They transport drugs and metabolites into urine or bile.
What are the factors affecting membrane transportation?
Molecule size
The size of a molecule influences its ability to pass through biological membranes. Generally, smaller molecules take short time to cross membranes compared to large molecules.
Lipid solubility
Lipid-soluble molecules can diffuse easily across membranes more than hydrophilic molecules. Lipid solubility refers to how well a molecule can dissolve in lipid-based environments.
Concentration gradient
The concentration gradient or different concentration in membrane influences the direction and rate of membrane transport.
Why we study membrane transport mechanisms?
- To learn basic biological processes like metabolism and cellular communication.
- To understand and treat diseases.
- To designing drugs and therapies.
- To understand drug delivery systems.
These are the basics answer of why we study membrane transportation mechanisms in pharmacy.
MCQ
1) What is the study of drug movement across the body:
- A) Pharmacodynamics
- B) Pharmacology
- C) Pharmacokinetics
- D) Pharmacogenomics
Answer: C) Pharmacokinetics
2) Which of the following is a mechanism of passive transportation:
- A) Active diffusion
- B) Facilitated diffusion
- C) Primary active transport
- D) Secondary active transport
Answer: B) Facilitated diffusion
3) Movement of molecules from an area of higher concentration to lower concentration called:
- A) Osmosis
- B) Filtration
- C) Facilitated diffusion
- D) Active transport
Answer: C) Facilitated diffusion
4) What type of transportation requires metabolic energy to move molecules against the concentration gradient?
- A) Passive diffusion
- B) Facilitated diffusion
- C) Filtration
- D) Active transport
Answer: D) Active transport
5) Which of the following is an example of primary active transportation?
- A) Sodium-potassium pump
- B) Glucose transporter
- C) Aquaporin channel
- D) Chloride channel
Answer: A) Sodium-potassium pump
6) In which direction do molecules move in symport?
- A) Same direction
- B) Opposite direction
- C) Random direction
- D) Circular direction
Answer: A) Same direction
7) Process of water molecules crossing a semipermeable membrane called:
- A) Filtration
- B) Osmosis
- C) Active transport
- D) Passive diffusion
Answer: B) Osmosis
8) Which type of drugs can diffuse more through biological membranes?
- A) Hydrophilic drugs
- B) Large molecules
- C) Lipid-soluble drugs
- D) Charged molecules
Answer: C) Lipid-soluble drugs
9) Movement of ions or molecules in the opposite direction called:
- A) Symport
- B) Antiport
- C) Osmosis
- D) Facilitated diffusion
Answer: B) Antiport
FAQ’s
What is pharmacokinetics?
Ans: It is the study of drug movement across the body.
What are the important factors of pharmacokinetics?
Ans: Routes of administration, dose, time for action, duration and frequency of drug administration.
Define biological membrane.
Ans: It is a double-layer membrane composed of phospholipids, cholesterol and proteins.
Define membrane transportation.
Ans: It is the mechanism by which solutes pass through biological membranes.
What is passive transportation?
Ans: When a drug moves across the cell membrane following a concentration gradient known as passive transportation.
What are the mechanisms of passive transportation?
Ans: Passive diffusion, facilitated diffusion, filtration and osmosis.
Define active transportation in pharmacokinetics.
Ans: When molecules move from lower to higher concentration regions across the cell membrane by using energy called as active transportation.
What is the difference between the passive and active transportation?
Ans: Passive transportation is the movement of molecules along a concentration gradient without energy. But active transportation requires energy to move molecules against the concentration gradient.