Pharmacokinetics and Pharmacodynamics
Pharmacokinetics
This is when a drug is administered, it is first absorbed at the site and then absorbed into the bloodstream. It refers to the study of how a drug is absorbed, distributed, metabolized and eliminated withing the body.
Classification of Drugs
Agonist
A drug with affinity and intrinsic activity for the receptor and is able to activate the receptor upon binding. This meaning the drug binds with a receptir and results in an effect. An example is Acetylcholine
Partial Agonist
These are drugs that bind to and activate a given receptor but are only able to have a partial effiicacy at the receptor relative to the agonist. An example is Buprenorphine
Antagonist
A drug with affinity but with no intrinsic activity for the receptor, binding with the receptor without essentially activating the receptor. It counteracts the action of the receptor. An example would be Beta Blockers.
Therapeutic and/or side effects of drugs
Type of drug
There are different types of drugs and these produce many different responses
Method of Administration
The way in which medications are administered greatly affect how they work, the intensity and the duration. Some drugs can also only be administered a certain way.
The Dosage
The effects can vary a lot depending on how much is given or administered. A small dosage might have little to no effect on a patient. A higher dosage there may be different behavioural responses and in extreme cases it can cause death
Age
Children and the elderly might have more sensitivity to drugs
Mental state or capacity
The state of a persons mentality also has a really large effect on their response to a drug.
Tolerance
After some time, of using a drug a persons body becomes or develops a tolerance to the drug and in some cases the drug may become ineffective
Metabolism and Absorption
Each individual has a different metabolic rate which essentially means that some people break down food or substances faster than others. If a drug is metabolized fast then the person may not experience andy effect of the medication.
Pharmacodynamis
This is the pharmalogical effect of the drug molecule on the body, this being the biochemical and physiological effects of drugs and the mechanisms of their actions. It comprises usually of receptor binding or non-specific action which leads to a pharmalogical effect.
Receptor Classifications
Enzyme receptors
Situated on enzymes and inhibit their functions
Transport-carrier receptors
Situated on carriers in the cell membranes and also carry drugs across the cell membrane.
Storage receptors
These receptors are present in nerve endings
Plasma protein receptors
These receptors are situated on plasma proteins such as Albumin
Secondary Pathway receptors
Alpha Receptors
These are receptors that stimulate effector cells. These control physiological processes such as vasoconstriction, intestinal relaxation or pupil dilation. There are two types of alpha receptors : Alpha 1 and Alpha 2. These are mainly found in vascular smooth muscles or effector tissues.
Methoxamine is an alpha 1 agonist and Clonidine is an alpha 2 agonist.
Beta Receptors
This refers to a group of receptors that relax the effector cells. They control vasodilation and relaxation of uterine muscles. They also increase the heart rate. There are also three types of beta cells. Beta 1, beta 2 and beta 3 receptors.These receptors are mainly found in cardiac muscles and bronchi muscles. Albuterol is and example of a beta 1 and metoprolol is an example of beta 2.