Important terms in Pharmacology – Science of Drugs

Pharmacology

It is the science of drugs that deals with interaction of exo genously administered chemical molecules with living systems

Any single chemical substance which can produce a biological response is a drug.

Pharmacodynamics

What the drug does to the body.

This includes physiological and biochemical effects of drugs and their mechanism of action at organ.

Pharmacokinetics

What the body does to the drug .

This refers to movement of the drug in and alteration of the drug by the body, includes absorption, distribution, binding ,storage, bio transformation and excretion of the drug.

Pharmacotherapeutics

It is the application of pharmacological information together with knowledge of the disease for its prevention, treatment or cure.

Selection of the most appropriate drug dosage and duration of treatment taking into account the specific features of patient are a part of pharmacotherapeutics.

Clinical pharmacology

It is the scientific study of drugs in man.

It includes pharmacodynamic and pharmacokinetic investigation in healthy man and in patients.

Chemotherapy

It is the treatment of systemic infection malignancy with specific drugs that have selective toxicity for the infecting organism malignant cell.

Drugs in general can be divided into;

1.Pharmacodynamic agents -These are designed to have pharmacodynamic effects in the recipient .

2.Chemotherapeutic agents– These are designed to inhibit kill invading parasites malignant cell.

ROUTES OF DRUG ADMINISTRATION

LOCAL ROUTES

These can only be used for localized lesions, at accessible sites from where drug’s systemic absorption from these sites is minimal or absent.

Thus, high concentrations are attained at the desired site without exposing the rest of the body.

Eg: applied ointment or transdermal patch on skin.

1. Topical This refers to extemal application of the drug to the surface for localized area. It is often more convenient to the patient eg;lotion, ointment, cream, powder rinse, paints, drops, spray etc.

2. Deeper tissues Certain deep areas can be approached by using a syringe and needle, but the drug should be in such a form that systemic absorption is slow. E.g. intra-articular injection (hydrocortisone acetate in knee joint).

3. Arterial supply- In angiography anticancer drugs can be infused in femoral or brachial artery to localise the effect for limb malignancies

SYSTEMIC ROUTES

The drug administered through systemic routes is intended to be absorbed into the bloodstream.

1. Oral– emulsions, mixtures can be given orally.

Limitations -Action of drugs is slower and thus not suitable for emergencies.

Some drugs may cause nausea and vomiting

Some drugs are destroyed by digestive juices .

2. Sublingual (S.I.) or buccal– The tablet or pill containing the drug is placed under the tongue or crushed in the mouth and Spread over the buccal mucosa.

Only lipid soluble and non-irritating drugs can be administered like this.

Drugs given sublingually are -GTN, desamino-oxytocin.

3. Rectal -Certain irritant and unpleasant drugs can be put into rectum as suppositories for systemic effect.

This route can also be used when the patient is having recurrent vomiting or is unconscious.

4. Cutaneous -Highly lipid soluble drugs can be applied over the skin for slow and prolonged absorption.

5.Inhalation– Volatile liquids and gases are given by inhalation for systemic action of general anaesthetics.

Absorption takes place from the vast surface of alveoli-function is very rapid.

6. Nasal -The mucous membrane of the nose can readily absorb many drugs.

7.Parenteral– administration of drug by injection which takes the drug directly into the tissue fluid or blood without having to cross the interal mucosa.

Parenteral routes can be employed even in unconscious, uncooperative or vomiting patient.

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