Which method of drug administration involves using a needle and syringe?

The method of drug administration that involves using a needle and syringe is injected administration. This method allows for the direct introduction of medication into the body, typically either into muscle, vein, or under the skin. The use of a needle and syringe provides a means to bypass the digestive system, allowing for faster and more efficient absorption of the drug into the bloodstream.

In contrast, transdermal administration involves applying medication through the skin using patches, which do not require a needle. Oral administration refers to swallowing medication, where it must pass through the digestive tract before entering the bloodstream. Inhalation involves delivering medication directly into the lungs, often using devices like inhalers or nebulizers, which also do not involve needles. Each of these methods has unique mechanisms and impacts on how a drug is absorbed, distributed, metabolized, and eliminated from the body.