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Routes of drug administration is elaborated in this sqadia.com video. From their Introduction to topical routes of Drug administration and first pass effect all concepts are discussed in detail by Muhammad Usman.
The way by which illicit drugs can be administered or taken into the body are numerous. These routes include the oral route, transdermal, inhalation, and intravenous injection. A route of administration is a way of getting a drug onto or into the body. Very young or older adult patients might have difficulty swallowing. Choice of route of administration may be influenced by ease of administration, site of therapeutic action, desired onset and duration of action, quantity of drug to be administered, characteristics of metabolism and excretion, and toxicity.
Enteral Route of Drug Administration
Oral route is the most common route of drug administration. It is mostly used for the neutral drugs. It may be in the form of tablets, capsules, syrup, emulsions or powders. Sublingual route involves tablets placed under the tongue or between cheeks or Gingiva. The drug should be lipid soluble and small. Drugs in solid forms such as suppositories or in liquid forms such as enema are given by this route. This route is mostly used in old patients. An oral drug might be too readily metabolized by the liver and eliminated from the body. Nausea and vomiting or severe acute illness in the GI tract make patient unable to take oral drugs.
Parenteral Routes of Drug Administration
Parenteral administration is injection or infusion by means of a needle or catheter inserted into the body. The IV route is the fastest method for delivering systemic drugs. It can provide fluids, electrolytes, and nutrition. It provides higher concentration of drug to bloodstream or tissues. Intramuscular (IM) and subcutaneous routes of administration are convenient ways to deliver medications. For intramuscular (IM) and subcutaneous routes of administration, the injection site needs to be “prepped” using alcohol wipe. Correct syringe, needle, and technique must be used. Administer medications below the skin into the subcutaneous fat.
Topical Routes of Drug Administration
Topical administration is the application of a drug directly to the surface of the skin. Includes administration of drugs to any mucous membrane, eyes, nose, ears, lungs, vagina, colon, and urethra. Ocular administration is the application of a drug to the eye. Conjunctival administration is the application of a drug to the conjunctival mucosa or lining of the inside of the eyelid. Nasal administration is the application of a drug into the passages of the nose. Otic administration is the application of a drug to the ear canal.
First Pass Effect
Drugs take different time durations after injection using different routes to perform their actions. This time delay is important, oral route has controlled release time, thus depot or reservoir preparation may be made e.g. penicillin for rheumatic fever. Usage of drug depends on its physical properties, chemical properties, speed of action, need and bypass effect. The first-pass effect is the term used for the hepatic metabolism of a pharmacological agent when it is absorbed from the gut and delivered to the liver via the portal circulation.