Reason For Drug Resistance

Drugs are defined as chemical substances that are used to prevent or cure diseases in humans, animals and plants. The activity of a drug is its pharmacological effect on the subject (person).
Drugs act by interfering with biological processes, so no drug is completely safe. All drugs can act as poisons if taken in excess. For example, overdoses of paracetamol can cause coma and death. In addition to their beneficial effects, most drugs have non-beneficial biological effects. Aspirin, which is commonly used to alleviate headaches, may also cause gastric irritation and bleeding. The non-beneficial effects of some drugs, such as cocaine and heroin, are so undesirable that the use of these drugs has to be strictly controlled by legislation. These

Resistance happens when a drug is no longer effective in controlling a medical condition. Resistance arises for many reasons, for example the effectiveness of barbiturates (used to cure mild seizures and sleep disorders) often decreases when used repeatedly because taking it repeatedly causes the body to increase its production in the liver of mixed function oxidases that metabolise the drug, therefore reducing the drug’s effectiveness. An increase in the rate of production of an enzyme that metabolises the drug is a common reason for drug resistance.
Another reason for drug resistance is the down-regulation of receptors (decrease in the number of receptors). Down-regulation happens when the receptors are stimulated repeatedly which causes the receptor to be broken down. This results in the drug being less effective because there are fewer receptors available for it to act on.
Drug resistance may also be due to the high amount of drug resistant strains of microorganisms. These strains arise naturally and can multiply very quickly and can become the currently predominant strain of that microorganism, for example antimalarial drug are less effective now because of an increase in the amount of drug resistant strains of the malaria

Dosage forms usually are made up of the active compound and other ingredients known as excipients. Excipients can have many functions, they can act as fillers, lubricants, binders, preservatives and antioxidants. A change in the nature of the excipients can significantly affect the stability of the active ingredient as well as its release from the dosage form. Changes in the preparation (the way the compound is made) of the active compound like the use of a different solvent for purification, can affect its bioavailability
(The fraction of the dose of a drug that is found in general circulation around the body. It is influenced by such factors such as Absorption, Distribution, Metabolism and Elimination (ADME). Bioavailability is not constant but varies with the body’s physiological condition.) and in turn its effectiveness as a