What primarily determines the method of drug administration?

The method of drug administration is primarily determined by the required speed of absorption because different routes of administration lead to varying rates at which a drug enters the bloodstream and takes effect. For instance, intravenous (IV) administration allows for immediate absorption and is often used in emergencies when rapid action is necessary. Conversely, oral administration may be slower due to the need for the drug to pass through the digestive system before entering circulation.

While the drug's chemical composition also influences its administration method, it is not the primary factor. Some drugs can be effective when taken orally or intravenously, but the decision on which method to use is often based on how urgently the effect is needed.

Patient preference can be a consideration in selecting a method of administration, but it typically comes after determining the required speed and effectiveness based on the clinical context. Likewise, while a physician's recommendation is essential, it usually reflects their clinical judgment about the urgency of drug action rather than being a standalone factor. Therefore, the speed of absorption most significantly dictates the choice of administration route in practice.