Routes Of Drug Administration PDF

ROUTES OF DRUG ADMINISTRATION BY DR. UDUAK PETER ISE DEPARTMENT OF PHARMACOLOGY AND TOXICOLOGY BINGHAM UNIVERSITY KARU, NASARAWA, NIGERIA. INTRODUCTION Most drugs can be administered by a variety of routes. The choice of appropriate route in a given situation...

ROUTES OF DRUG ADMINISTRATION BY DR. UDUAK PETER ISE DEPARTMENT OF PHARMACOLOGY AND TOXICOLOGY BINGHAM UNIVERSITY KARU, NASARAWA, NIGERIA. INTRODUCTION Most drugs can be administered by a variety of routes. The choice of appropriate route in a given situation depends both on drug as well as patient-related factors. Mostly, common sense considerations, feasibility and convenience dictate the route to be used. Factors Governing Choice of Route Physical and chemical properties of the drug (solid/liquid/ gas; solubility, stability, pH, irritancy). Site of desired action-localized and approachable or generalized and not approachable. Rate and extent of absorption of the drug from different routes. Effect of digestive juices and first pass metabolism on the drug. Rapidity with which the response is desired (routine treatment or emergency). Accuracy of dosage required (i.v. and inhalational can provide fine tuning). Condition of the patient(unconscious, vomiting).  Routes can be broadly divided into those for (a) Local action and (b) Systemic action. LOCAL ROUTES These routes can only be used for localized lesions at accessible sites and for drugs whose 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. Systemic side effects or toxicity are consequently absent or minimal. Topical This refers to external application of the drug to the surface for localized action. It is often more convenient as well as encouraging to the patient. Drugs can be efficiently delivered to the localized lesions on skin, oropharyngeal/ nasal mucosa, eyes, ear canal, anal canal or vagina in the form of lotion, ointment, cream, powder, rinse, paints, drops, spray, lozenges, suppositories or pessaries. Deeper Tissues Certain deep areas can be approached by using a syringe and needle, but the drug should be such that systemic absorption is slow, e.g. intra-articular injection (hydrocortisone acetate), infiltration around a nerve or intrathecal injection (lidocaine), retrobulbar injection (hydrocortisone acetate). Arterial Supply Close intra-arterial injection is used for contrast media in angiography Anticancer drugs can be infused in femoral or brachial artery to localise the effect for limb malignancies. SYSTEMIC ROUTES Oral Sublingual Rectal route Subcutaneous Intradermal (e.g. BCG vaccine) Intravenous Intramuscular Intraperitoneal Inhalation Volatile liquids and gases are given by inhalation for systemic action, e.g. general anesthetics. Absorption takes place from the vast surface of alveoli- action is very rapid. When administration is discontinued the drug diffuses back and is rapidly eliminated in expired air. Thus, controlled administration is possible with moment to moment adjustment. Irritant vapours (ether) cause inflammation of respiratory tract and increase secretion. Parenteral Routes This refers to administration by injection which takes the drug directly into the tissue fluid or blood without having to cross the intestinal mucosa. The limitations of oral administration are circumvented. Drug action is faster and surer (valuable in emergencies). Gastric irritation and vomiting are not provoked. Parenteral routes can be employed even in unconscious, uncooperative or vomiting patient. There are no chances of interference by food or digestive juices. Liver is bypassed. Disadvantages Disadvantages of parenteral routes are-the preparation has to be sterilized and is costlier, the technique is invasive and painful, assistance of another person is mostly needed (though self injection is possible, e.g. insulin by diabetics), there are chances of local tissue injury and, in general, parenteral route is more risky.