Ephedrine: A phenethylamine found in EPHEDRA SINICA. PSEUDOEPHEDRINE is an isomer. It is an alpha- and beta-adrenergic agonist that may also enhance release of norepinephrine. It has been used for asthma, heart failure, rhinitis, and urinary incontinence, and for its central nervous system stimulatory effects in the treatment of narcolepsy and depression. It has become less extensively used with the advent of more selective agonists.Ephedra: A plant genus of the family Ephedraceae, order Ephedrales, class Gnetopsida, division Gnetophyta.Phenylpropanolamine: A sympathomimetic that acts mainly by causing release of NOREPINEPHRINE but also has direct agonist activity at some adrenergic receptors. It is most commonly used as a nasal vasoconstrictor and an appetite depressant.Anesthesia, Obstetrical: A variety of anesthetic methods such as EPIDURAL ANESTHESIA used to control the pain of childbirth.Anesthesia, Spinal: Procedure in which an anesthetic is injected directly into the spinal cord.Pseudoephedrine: A phenethylamine that is an isomer of EPHEDRINE which has less central nervous system effects and usage is mainly for respiratory tract decongestion.Ephedra sinica: A plant species of the family Ephedraceae, order Ephedrales, class Gnetopsida, division Gnetophyta. It is a source of EPHEDRINE and other alkaloids.Hypotension: Abnormally low BLOOD PRESSURE that can result in inadequate blood flow to the brain and other vital organs. Common symptom is DIZZINESS but greater negative impacts on the body occur when there is prolonged depravation of oxygen and nutrients.Sympathomimetics: Drugs that mimic the effects of stimulating postganglionic adrenergic sympathetic nerves. Included here are drugs that directly stimulate adrenergic receptors and drugs that act indirectly by provoking the release of adrenergic transmitters.Metaraminol: A sympathomimetic agent that acts predominantly at alpha-1 adrenergic receptors. It has been used primarily as a vasoconstrictor in the treatment of HYPOTENSION.Cesarean Section: Extraction of the FETUS by means of abdominal HYSTEROTOMY.Ritodrine: An adrenergic beta-2 agonist used to control PREMATURE LABOR.Doping in Sports: Illegitimate use of substances for a desired effect in competitive sports. It includes humans and animals.Phenylephrine: An alpha-1 adrenergic agonist used as a mydriatic, nasal decongestant, and cardiotonic agent.Vasoconstrictor Agents: Drugs used to cause constriction of the blood vessels.Central Nervous System Stimulants: A loosely defined group of drugs that tend to increase behavioral alertness, agitation, or excitation. They work by a variety of mechanisms, but usually not by direct excitation of neurons. The many drugs that have such actions as side effects to their main therapeutic use are not included here.Anesthesia, Epidural: Procedure in which an anesthetic is injected into the epidural space.