Route of administration in the context of "Intravenous therapy"

Medication (also called medicament, medicine, pharmaceutical drug, medicinal product, medicinal drug or simply drug) is a drug used to diagnose, cure, treat, or prevent disease. Drug therapy (pharmacotherapy) is an important part of the medical field and relies on the science of pharmacology for continual advancement and on pharmacy for appropriate management.

Drugs are classified in many ways. One of the key divisions is by level of control, which distinguishes prescription drugs (those that a pharmacist dispenses only on the medical prescription) from over-the-counter drugs (those that consumers can order for themselves). Medicines may be classified by mode of action, route of administration, biological system affected, or therapeutic effects. The World Health Organization keeps a list of essential medicines.

Smoking is a human behavior which involves the combustion of a substance, usually plant material, and the inhalation of resulting fumes. Today smoking is mostly practiced by rolling the dried leaves of the tobacco plant into a cigarette. Other forms of tobacco smoking include the use of a smoking tobacco with a pipe or cigar, or using a bong. Cigarette smokers almost always inhale the smoke; most pipe and cigar smokers do not inhale.

Smoking is primarily practiced as a route of administration for psychoactive chemicals because the active substances within the burnt, dried plant leaves (or other chemical) can vaporize into a gaseous state and be delivered into the respiratory tract, where they are rapidly absorbed into the bloodstream through the lungs and can reach the central nervous system. In the case of tobacco smoking, these active substances are a mixture of aerosol particles that include the pharmacologically active alkaloid nicotine, which stimulates the nicotinic acetylcholine receptors in the brain, and other non-psychoactive chemicals that result from combustion. Other notable drugs inhaled via smoking include tetrahydrocannabinol (from cannabis), morphine (from opium) cocaine (from crack), and methamphetamine. Designer drugs, or "research chemicals", can also be smoked.

Absorption is the journey of a drug travelling from the site of administration to the site of action.

The drug travels by some route of administration (oral, topical-dermal, etc.) in a chosen dosage form (e.g., tablets, capsules, or in solution). Absorption by some other routes, such as intravenous therapy, intramuscular injection, enteral nutrition, is even more straightforward and there is less variability in absorption and bioavailability is often near 100%. Intravascular administration does not involve absorption, and there is no loss of drug. The fastest route of absorption is inhalation.

A psychoactive drug, psychopharmaceutical, mind-altering drug, consciousness-altering drug, psychoactive substance, or psychotropic substance is a chemical substance that alters psychological functioning by modulating central nervous system (CNS) activity. Psychoactive and psychotropic drugs both affect the brain, with psychotropics sometimes referring to psychiatric drugs or high-abuse substances, while “drug” can have negative connotations. Novel psychoactive substances are designer drugs made to mimic illegal ones and bypass laws.

Psychoactive drug use dates back to prehistory for medicinal and consciousness-altering purposes, with evidence of widespread cultural use. Many animals intentionally consume psychoactive substances, and some traditional legends suggest animals first introduced humans to their use. Psychoactive substances are used across cultures for purposes ranging from medicinal and therapeutic treatment of mental disorders and pain, to performance enhancement. Their effects are influenced by the drug itself, the environment, and individual factors. Psychoactive drugs are categorized by their pharmacological effects into types such as anxiolytics (reduce anxiety), empathogen–entactogens (enhance empathy), stimulants (increase CNS activity), depressants (decrease CNS activity), and hallucinogens (alter perception and emotions). Psychoactive drugs are administered through various routes—including oral ingestion, injection, rectal use, and inhalation—with the method and efficiency differing by drug.

Psilocybin, also known as 4-phosphoryloxy-N,N-dimethyltryptamine (4-PO-DMT), is a naturally occurring tryptamine alkaloid and investigational drug found in more than 200 species of mushrooms, with hallucinogenic and serotonergic effects. Effects include euphoria, changes in perception, a distorted sense of time (via brain desynchronization), and perceived spiritual experiences. It can also cause adverse reactions such as nausea and panic attacks.

Psilocybin is a prodrug of psilocin. That is, the compound itself is biologically inactive but quickly converted by the body to psilocin. Psilocybin is transformed into psilocin by dephosphorylation mediated via phosphatase enzymes. Psilocin is chemically related to the neurotransmitter serotonin and acts as a non-selective agonist of the serotonin receptors. Activation of one serotonin receptor, the serotonin 5-HT_2A receptor, is specifically responsible for the hallucinogenic effects of psilocin and other serotonergic psychedelics. Psilocybin is usually taken orally. By this route, its onset is about 20 to 50 minutes, peak effects occur after about 1 to 2 hours, and its duration is about 4 to 6 hours.