The routes of drug administration can vary widely, but they are often categorized into five main methods. Here they are in a general order based on the speed of onset of action, though the order can vary based on specific clinical scenarios or contexts:
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Intravenous (IV) - This route delivers drugs directly into the bloodstream, providing rapid effects, which is ideal for emergencies or when immediate action is necessary.
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Intramuscular (IM) - Drugs administered via this route are injected into a muscle, where they are absorbed into the bloodstream relatively quickly, although not as fast as IV.
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Subcutaneous (SC) - This route involves injecting drugs into the tissue layer between the skin and muscle. The absorption is slower compared to IM due to fewer blood vessels in the subcutaneous tissue.
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Oral (PO) - Oral administration is the most common method and involves swallowing the drug. It typically has a slower onset as the drug must be absorbed through the gastrointestinal tract.
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Topical - This method applies drugs directly onto the skin or mucous membranes. It is generally used for localized effects and has variable absorption depending on the drug and site of application.
Other routes include inhalation, transdermal, and rectal, each with its own specific applications and absorption characteristics.