Routes of Drugs administrationDefinition: The way through which a drug makes enterance into body or applies on the various surface of the body is called the routes of drug administration.

Classification of routes of drug administration• A. Systemic Routes: It can be classified into two routes;• 1. Enteral or Alimentary routes:• (a) Sublingual or Buccal, beneath the tongue.• (b) Oral-through the mouth • (c) Rectal - Administer through the rectum.• 2. Parenteral Route • a) Injection - * Subcutaneous (SC) - Beneath the skin. • * Intracutaneous (IC) - inside the skin. • * Intra-arterial (IA) - within the artery. • * Intravenous (IV) - within the vein.

* Intramuscular (IM) - within the muscle. * Intraarticular (IArt) - within the article.

• * Intraperitoneal (IP) - within the lower abdomen. • * Intraventricular - within the ventricle. • * Intrathecal - within the spinal cord. • * Intracrdiac - within the heart. • * Intrapleural - within the pleural • * Intramedullary - within the medulla of longata. • * Intralesional - within the lesion.• b) Inhalation / inhaler.• * Gas eg. : Volatile anesthetic: N2O, Chloroform. • * Aerosol: eg Beta adrenoceptor agonist: Salbutamol - A Bronchodilator.• * Powder: Na+ chromoglycate.

• B. Local Routes: Applied locally and action is continued to that particular area. • 1. Topical application: Ointment, paste, drops, powder, lotion etc. • a) Skin injunction (By rubbing of drug on skin)• b) To mucous membrane of nose, urethra, rectum, & anal canal .• c) To eye and ear.

Choice of route of drug administration: In the choice of route of drug administration, knowledge of advantages and disadvantages of different routes is of primary important. So advantages and disadvantages of some routes are arranged bellow:

Oral Route • Advantages:• 1. Safest, most convenient and most economical (tablet &

capsule as exact dose).• 2. Painless routes• 3. Self medication is possible.• 4. Prolong action can be obtained by delaying absorption.(by

various technology)• 5. Drugs need not to be sterile or highly purified.• 6. Free from anxiety for prickling needle, associated with pain

and may occur sepsis • 7. Easy way and patient can take medicine without

interrupting his activity.• 8. Hypersensitivity reaction is less. (Hypersensitivity is the

over sensitive state to the exposure of any kind of allergens by which it was produced specific antibody previously)

• Emesis can be done incase of oral poisoning

Oral Route, cont. • Disadvantages:• 1. Limited absorption of some drug because of their physical

characteristics eg water solubility or shape and size.• 2. Emesis as a result of irritation to the gastric mucosa.• 3. Destruction of some drugs by digestive enzyme or by acid.• 4. Irregularities in absorption in the presence of food or other

drugs.• 5. Necessary for co-operation of patient is need.• 6. Drug may metabolized by the enzyme of intestinal flora, mucosa

or liver before they gain access to the general circulation.• 7. Delayed absorption so not suitable for emergency cases.• 8. Unpleasant and hydrophobic drug administration is unsuitable.

Required taste masking of bitter drugs.• 9. Not suitable for unconscious patient. They will not be able to

shawllow.• 10. Drugs having first pass metabolism are unsuitable eg .

Testosterone.

Intravenous Route Advantages over oral route:• 1. It is more suitable for the drug to be delivered in

active form.• 2. Availability is usually more, complete, rapid, and

extensive.• 3. Effective doses can be more accurately delivered.• 4. In emergency therapy and when a patient is

unconscious, uncooperative or unable to retain anything by mouth.

• 5. Large volume, unpleasant and irritant solution can be given, as the venous/veins walls are less sensitive and so less irritation.

• 6. Diarrhea, vomiting can be overcome.• 7. By pass the drug modification by digestive juice,

hepatic enzymes.• 8. It is possible to adjust dose according to response

Intravenous Route Disadvantages:• 1. Painful procedure • 2. Self-medication is difficult.• 3. Strict aseptic measures, special technique and skillness are

essentials.• 4. Risks like infection, hypersensitivity reaction, pyrogenic

reaction, local venous thrombosis & hemolysis may occur (thrombosis-the formation or presence of thrombus)

• 5. Leakage of drug outside the vein can produce irritation.• 6. Over dose have immediate effects, it is impossible to reverse.

But incase of oral routes vomiting can possible.• 7. Chance of injury to surrounding nerves and vessels.• 8. Drug must be water soluble.• 9. Short duration of action, excretion rapid, expensive. • 10. No retreat possible if once drug is administered.• 11. Drug in oily vehicles or those that precipitate blood constituents or

hemolyse erythrocyte should not be administered.

Sublingual/Buccal Route Some drugs are taken as smaller tablets

which are held under the tongue. This is known as sublingual route.

• Advantages – rapid absorption– Achieve drug stability– avoid first-pass effect

Sublingual/Buccal

• Disadvantages– Inconvenient to keep drug under tongue.– Applicable only for small doses– unpleasant taste drugs are not suitable for

this route.

Advantages:1.Suitable for unconscious patients and children 2. Avoid nauseous or vomiting conditions 5. Good for drugs affecting the bowel such as laxatives

Disadvantages:1. Irritating drugs contraindicated2.Absorption may be variable

Rectal Route