Nicotine, cocaine, and organic solvents such as airplane glue and gasoline are inhaled, as are a variety of prescription drugs and hormone treatments. Inhalation methods take advantage of the rich vascularization of the nose and lungs to convey drugs directly into the bloodstream. Typically is moderate to fast acting. Examples include: nasal absorption, inhaled powders and sprays, and smoking. 

Inhalation of a drug examples, mechanisms, and typical speed of effects.

The mechanisms that make the movement of substances from blood vessels into brain cells more difficult than exchanges in other body organs, thus affording the brain greater protection from exposure to some substances found in the blood 

Bowdoin College

The amount of drug that reaches the brain and the speed with which is starts acting are determined in part by the drug's route of administration. 
- bioavailable
- biotransformation
- pharmacokinetics
- blood brain barrier

Drugs are administered and eliminated in many different ways

Collective name for all the factors that affect the movement of a drug into, through, and out of the body.

Pharmacokinetics

Breedlove, S. & Watson, N. (2017). Behavioral neuroscience, eighth edition. Oxford University Press.

Behavioral Neuroscience 8th Edition

The process in which enzymes convert a drug into a metabolite that is itself active, possibly in ways that are substantially different from the actions of the original substance.

Biotransformation

Blood-brain barrier

Humans have devised a variety of techniques for introducing substances into the body.
- ingestion 
- inhalation
- peripheral injection
- central injection

The routes of administration of drugs  

Referring to a substance, usually a drug, that is present in the body in a form that is able to interact with physiological mechanisms.

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