Routes Of Drug Administration - PDF

# Routes of Drug Administration ## Contents * Definition * Factors affecting route * Classification * Local Routes and their advantages and disadvantages * Enteral Routes and their advantages and disadvantages * Parenteral Routes and their advantages and disadvantages ## Definition A route of ad...

# Routes of Drug Administration ## Contents * Definition * Factors affecting route * Classification * Local Routes and their advantages and disadvantages * Enteral Routes and their advantages and disadvantages * Parenteral Routes and their advantages and disadvantages ## Definition A route of administration is the path by which a drug or substance is brought into contact with the body. ## Factors affecting the choice of route 1. Physical and chemical properties of the drug 2. Site of desired action 3. Rate and extent of absorption from different routes 4. Effect of digestive juices and first pass metabolism on the drug 5. Rapidity with which the response is desired 6. Accuracy of dosage required 7. Condition of patient ## Classification | | | | ---------------- | ---------------- | | **Route** | | | **Local** | **Systemic** | | **Topical** | | | **Deeper tissues** | **Enteral** | | **Arterial supply** | **Parenteral** | ## Local Routes * These can only be used for localised lesions at accessible sites & for drugs whose systemic absorption from these sites is minimal. E.g. GTN applied as ointment * High concentrations are attained at desired site without exposing rest of body. The local routes are: 1. Topical 2. Deeper tissues 3. Arterial Supply ## Topical route * This refers to external application of the drug to the surface for localised action. * (a) Skin: Drug is applied as ointment, cream, lotion, paste, powder, dressing etc. ## Deeper tissues * Another local/ Parenteral route of administration though invasive * The drug is in such state that absorption is slow and systemic absorption is minimal * e.g. Hydrocortisone acetate in knee joint/ retrobulbar injection ## Arterial Supply * Local but Parenteral route attained by drug with minimal systemic absorption * E.g. 1) Intra-arterial injection for contrast media in angiography; 2)anti-cancer drugs in femoral artery/ brachial artery to localise malignancies in limbs ## Enteral Routes * Definition: When drug is placed directly in the GI tract. | | | -------- | | **Enteral** | | **Oral** | | **Buccal/ Sublingual** | | **Rectal** | ## Oral Route * Oral administration is designated as per os (PO), which means to administer 'by mouth'. * The medication is swallowed, and the drug is absorbed from the stomach and small intestines. ## Advantages of Oral admin. * Safest route * Commonest * Convenient * No skill required, self medication * Painless, & acceptable * Cost effective * No maximal/strict sterilization required ## Disadvantages of Oral admin. * Slow absorption→ delayed onset of action Not suitable for emergencies * Unpalatable and irritant drugs not administered e.g. Chloramphenicol * May cause nausea and vomiting * Absorption of drugs → variable and erratic e.g. Streptomycin not absorbed * Interactions of prescribed drug with food and other drugs affects absorption * Administration difficult in uncooperative & unconscious patients * Some drugs are destroyed by gastric secretions e.g. Insulin, ACTH * Some drugs are undergo extensive first pass metabolism in the liver e.g. Lidocaine, GTN, testosterone ## Sublingual/ Buccal * Some drugs are taken as smaller tablets which are held in the mouth (buccal tablet) or under the tongue (sublingual tablet). ### SUBLINGUAL ROUTE | ADVANTAGES | DISADVANTAGES | | ------------------------------------- | ---------------------------------- | | Economical | Unpalatable & bitter drugs | | Drug absorption is quick | Irritation of oral mucosa | | First-pass avoided | Large quantities not given | | Quick termination- Spit off | | | Can be self administered | |