Inhalation is a drug administration route in which a drug or inhalant is smoked. Inhalation is effectively used medically for several anesthetics. The onset of this drug administration route is quite rapid due to the fact that there are capillaries located in the lungs, making it easy for the drug to quickly enter the bloodstream. Once the drug is in the bloodstream, it takes approximately five to eight seconds for the drug to reach the brain.
Problems with Inhalation
Although inhalation is an effective method of drug administrations, there are three factors that must be kept into consideration with medically using this drug administration method.
1. Drugs and materials must not be irritating to the mucous membranes and lungs.
2. Controlling the dosage may be more difficult than other drug administration methods.
3. The drug must be administered until the desired effect is met. 
- Hart, Carl. Drugs, Society, and Human Behavior. 12th. McGraw-Hill Humanities, 2008. Print.