Foundations of medicine: Introduction to Pharmacology

Clinical pharmacology teaches the mechanisms and effects (both beneficial and adverse) of drugs that doctors prescribe for their patients: why drugs work and how to prescribe them.

A drug can be defined as a medicine or other substance which has a physiological effect when ingested or otherwise introduced into the body.

 A medicine can be defined as an active substance with a direct effect in the diagnosis, cure, mitigation, treatment or prevention of disease.

Meanwhile a placebo is an inactive substance administered as though it is a drug, but which has no therapeutic effect (other than pleasing the patient)

• Efficacy- how effective is the drug at having the desired effect
• Potency- how powerful is the drug, how much is needed to be perscribed to reach the desired effect
• Safety- how many patients have unwanted side effects from the drug
• Variability- what proportion of patients have the desired response when given the drug
• selectivity- how selectivly does the drug act on its molecular target- does it effect other receptors
• Bioavailability- how much of the drug is actually absorbed

• An agonist is a substance that is designed to revoke a response in the body.
• An Antagonist reduces a response in the body

The therapeutic index is a  measurement of the relative safety of a drug. It is a comparison of the amount of the drug that causes the therapeutic effect to the amount that is toxic. If a drug has a very high theraputic index it means that the effective theraputic dose will be very unlikley to cause toxic side effects.

Adherance can be thourght of as the act of taking medication on schedule or taking medication as prescribed, to achieve the desired health benefit i.e. following a healthcare professional's advice.

factors effecting adherance can include:

• Complexity of the regimen, which can lead to mistakes in doses, taking either too much or forgetting to take any
• Failure of the patient to understand the importance of adherence, with treatments perceived as ineffective or unsafe
• The patient's perception of barriers to adherence e.g. an unwillingness to make lifestyle changes to accommodate a recommended treatment regimen

In agonists as the drug dose increases the theraputic response increases,however once the drug has reached its maximum response the theraputic effect will stay the same as the dose is increased further. This is because all of the receptors available for the drug to act on will already be in use.