Anorectic

An anorectic or anorexic is a drug which reduces appetite, resulting in lower food consumption, leading to weight loss. These substances work by affecting the central nervous system or certain neurotransmitters to create a feeling of fullness or reduce the desire to eat. The understanding of anorexiant effects is crucial in the development of interventions for weight management, eating disorders, and related health concerns. The anorexiant effect can be induced through diverse mechanisms, ranging from hormonal regulation to neural signaling. Ghrelin, leptin, and peptide YY are among the hormones involved in appetite control. Additionally, neurotransmitters such as serotonin and dopamine in the central nervous system contribute significantly to the regulation of food intake.

By contrast, an appetite stimulant is referred to as orexigenic.

The term is (from the Greek ἀν- an- without and ὄρεξις órexis appetite), and such drugs are also known as anorexigenic, anorexiant, or appetite suppressant.

History
Used on a short-term basis clinically to treat obesity, some appetite suppressants are also available over-the-counter. Several appetite suppressants are based on a mix of natural ingredients, mostly using green tea as its basis, in combination with other plant extracts such as fucoxanthin, found naturally in seaweed. Drugs of this class are frequently stimulants of the phenethylamine family, related to amphetamine.

The German and Finnish militaries issued amphetamines (Pervitin) to soldiers commonly during the Second World War. Similarly, the UK military was supplied with more than 72 million Benzedrine tablets and the US military with an approximately equal amount for situations, in which fatigue was not deemed to be an acceptable option. Following the war, large amphetamine surpluses were redirected for use on the black and the civilian market. Indeed, amphetamine itself was sold commercially as an appetite suppressant until it was outlawed in most parts of the world in the late 1950s because of safety issues. Many amphetamines produce side effects, including addiction, tachycardia and hypertension, making prolonged unsupervised use dangerous.

Public health concerns
Epidemics of fatal pulmonary hypertension and heart valve damage associated with pharmaceutical anorectic agents have led to the withdrawal of products from the market. This was the case with aminorex in the 1960s, and again in the 1990s with fenfluramine (see: Fen-phen). Likewise, association of the related appetite suppressant phenylpropanolamine with hemorrhagic stroke led the Food and Drug Administration (FDA) to request its withdrawal from the market in the United States in 2000, and similar concerns regarding ephedrine resulted in an FDA ban on its inclusion in dietary supplements in 2004. A Federal judge later overturned this ban in 2005 during a challenge by supplement maker Nutraceuticals. It is also debatable as to whether the ephedrine ban had more to do with its use as a precursor in methamphetamine manufacture rather than health concerns with the ingredient as such.

Non-pharmacological alternatives
Weight loss effects of water have been subject to some scientific research as a potential non-pharmacological approach. Drinking water prior to each meal may help in appetite suppression. Consumption of 500 mL of water 30 minutes before meals has been correlated with modest weight loss (1 –) in obese men and women over a period of 8 to 12 weeks.

Refeeding syndrome
Refeeding syndrome (RFS) is a metabolic disturbance which occurs as a result of reinstitution of nutrition in people and animals who are starved, severely malnourished, or metabolically stressed because of severe illness. When too much food or liquid nutrition supplement is eaten during the initial four to seven days following a malnutrition event, the production of glycogen, fat and protein in cells may cause low serum concentrations of potassium, magnesium and phosphate. The electrolyte imbalance may cause neurologic, pulmonary, cardiac, neuromuscular, and hematologic symptoms—many of which, if severe enough, may result in death.

Refeeding syndrome can occur when someone does not eat for several days at a time usually beginning after 4–5 days with no food.

Individuals with drug abuse who begin to reintroduce normal eating habits after a period of malnutrition may be at increased risk for refeeding syndrome.

List of anorectics
Numerous pharmaceutical compounds are marketed as appetite suppressants.

The following drugs are listed as "centrally-acting antiobesity preparations" in the Anatomical Therapeutic Chemical Classification System:
 * Amfepramone (also known as diethylpropion)
 * Bupropion and naltrexone (combination)
 * Cathine
 * Clobenzorex
 * Dexfenfluramine† (the D -enantiomer of fenfluramine; withdrawn for the same reason as its racemate)
 * Ephedrine (combinations)
 * Etilamfetamine
 * Fenfluramine† (one of the two components [the other being phentermine] of Fen-phen. Since discontinued to its potential for causing valvulopathies and pulmonary hypertension)
 * Lorcaserin (withdrawn in the United States by the FDA due to an increased risk of cancer)
 * Mazindol
 * Mefenorex
 * Phentermine
 * Sibutramine† (in some countries withdrawn from the market because of concerns regarding its cardiovascular effects)
 * Topiramate

The following are listed as appetite depressants by MeSH, an index of medical journal articles and books.
 * Benfluorex (removed from the market by the EMA due to increased risk of heart disease)
 * Butenolide
 * Diethylpropion
 * FG-7142
 * Phenmetrazine† (withdrawn in some countries due to the danger of addiction)
 * Phentermine
 * Phenylpropanolamine
 * Pyroglutamyl-histidyl-glycine
 * Sibutramine

Other compounds with known appetite suppressant activity include:
 * Amphetamine-Dextroamphetamine is known to hamper appetite. Amphetamine-Dextroamphetamine is used to treat Attention deficit hyperactivity disorder (ADHD) and is usually under the trade name "Adderall" or "Mydayis".
 * Amphetamine sulfate (also known as amfetamine) – US FDA-approved for the treatment of exogenous obesity under the brand name "Evekeo".
 * Methylphenidate
 * Cocaine
 * Caffeine
 * Glucomannan
 * Leptin
 * Lisdexamphetamine - US FDA approved for the treatment of binge-eating disorder in adults under the brand name "Vyvanse".
 * Methamphetamine hydrochloride – USFDA-approved for the treatment of obesity (as a short-term) under the brand name "Desoxyn".
 * Nicotine
 * Liraglutide as brand name Saxenda
 * Semaglutide (brand name Ozempic/Wegovy) GLP-1 agonist
 * Metformin
 * Opiates/opioids such as heroin, morphine, codeine, oxycodone, fentanyl, etc.