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Drugs that lower neurotransmission levels, reducing brain stimulation

Colloquially known as "downers", depressants or central depressants are drugs that lower neurotransmission levels, or depress or reduce arousal or stimulation in various areas of the brain. Depressants do not change the mood or mental state of others. Stimulants, or "uppers", increase mental or physical function, hence the opposite drug class from depressants are stimulants, not antidepressants. Depressants are widely used throughout the world as prescription medicines and illicit substances. Alcohol is a very prominent depressant. When depressants are used, effects often include ataxia, anxiolysis, pain relief, sedation or somnolence, cognitive or memory impairment, as well as, in some instances, euphoria, dissociation, muscle relaxation, lowered blood pressure or heart rate, respiratory depression, and anticonvulsant effects. Depressants also act to produce anesthesia. Cannabis may sometimes be considered a depressant due to one of its components, cannabidiol. The latter is known to treat insomnia, anxiety, and muscle spasms, similar to other depressive drugs. However, while tetrahydrocannabinol, another component, may slow brain function to a small degree while reducing reaction to stimuli, it is generally considered a stimulant and main psychoactive agent that can sometimes cause anxiety, panic, and psychosis instead. Other depressants can include drugs like Xanax (a benzodiazepine) and a number of opioids. Gabapentinoids like gabapentin and baclofen are depressants and have anticonvulsant, and anxiolytic effects. Most anticonvulsants like Lamotrigine and Phenytoin are depressants. Carbamates are depressants that are similar to barbiturates. Depressants exert their effects through a number of different pharmacological mechanisms, the most prominent of which include facilitation of GABA and inhibition of glutamatergic or monoaminergic activity. Other examples are chemicals that modify the electrical signaling inside the body, the most prominent of which are bromides and channel blockers.

An alcoholic beverage is a drink that contains alcohol (known formally as ethanol), an anesthetic that has been used as a psychoactive drug for several millennia. Ethanol is the oldest recreational drug still used by humans. Ethanol can cause alcohol intoxication when consumed. Alcoholic beverages are divided into three general classes for taxation and regulation of production: beers, wines, and spirits (distilled beverages). They are legally consumed in most countries around the world. More than 100 countries have laws regulating their production, sale, and consumption. The most common way to measure intoxication for legal or medical purposes is through blood alcohol content (also called blood alcohol concentration or blood alcohol level). It is usually expressed as a percentage of alcohol in the blood in units of mass of alcohol per volume of blood, or mass of alcohol per mass of blood, depending on the country. For instance, in North America a blood alcohol content of 0.10 g/dL means that there are 0.10 g of alcohol for every dL of blood (i. e., mass per volume is used there).

Barbiturates are effective in relieving the conditions that they are designed to address (insomnia, seizures). They are also commonly used for unapproved purposes, are physically addictive, and have serious potential for overdose. By the late 1950s, concerns over the mounting social costs associated with barbiturates, which were beginning to overshadow their perceived medical benefits, prompted a concerted effort to find alternative medications. Most people still using barbiturates today do so in the prevention of seizures or in mild form for relief from the symptoms of migraines.

A benzodiazepine (sometimes colloquially "benzo"; often abbreviated "BZD") is a drug whose core chemical structure is the fusion of a benzene ring and a diazepine ring. The first such drug, chlordiazepoxide (Librium), was discovered accidentally by Leo Sternbach in 1955 and made available in 1960 by Hoffmann–La Roche, who has also marketed the benzodiazepine diazepam (Valium) since 1963. Benzodiazepines enhance the effect of the neurotransmitter gamma aminobutyric acid (GABA) at the GABAA receptor, resulting in sedative, hypnotic (sleep inducing), anxiolytic (anti anxiety), anticonvulsant, and muscle relaxant properties; also seen in the applied pharmacology of high doses of many shorter acting benzodiazepines are amnesic dissociative actions. These properties make benzodiazepines useful in treating anxiety, insomnia, agitation, seizures, muscle spasms, alcohol withdrawal, and as a premedication for medical or dental procedures. Benzodiazepines are categorized as either short , intermediate , or long acting. Short and intermediate acting benzodiazepines are preferred for the treatment of insomnia; longer acting benzodiazepines are recommended for the treatment of anxiety. In general, benzodiazepines are safe and effective in the short term, although cognitive impairments and paradoxical effects such as aggression or behavioral disinhibition occasionally occur. A minority react reverse and contrary to what would normally be expected. For example, a state of panic may worsen considerably following intake of a benzodiazepine. Long term use is controversial due to adverse psychological and physical effects, decreasing effectiveness, physical dependence, and benzodiazepine withdrawal syndrome, following withdrawal after long term use. Due to adverse effects associated with the long term use of benzodiazepines, withdrawal from benzodiazepines generally leads to improved physical and mental health. The elderly are at an increased risk of experiencing both short and long term adverse effects. There is controversy concerning the safety of benzodiazepines in pregnancy. While they are not major teratogens, uncertainty remains as to whether they cause cleft palate in a small number of babies and whether neurobehavioral effects occur as a result of prenatal exposure; they are known to cause withdrawal symptoms in the newborn. Benzodiazepines can be taken in overdoses and can cause dangerous deep unconsciousness. However, they are much less toxic than their predecessors, barbiturates, and death rarely results when a benzodiazepine is the only drug taken; however, when combined with other central nervous system depressants such as alcohol and opiates, the potential for toxicity and fatal overdose increases. Benzodiazepines are commonly misused and taken in combination with other addictive drugs. In addition, all benzodiazepines are listed in Beers List, which is significant in clinical practice.

Cannabis is often considered either in its own unique category or as a mild psychedelic. The chemical compound tetrahydrocannabinol (THC), which is found in cannabis, has many depressant effects such as muscle relaxation, sedation, decreased alertness, and tiredness. Contrary to the previous statement, activation of the CB1 receptor by cannabinoids causes an inhibition of GABA, the exact opposite of what central nervous system depressants do.

Gamma Hydroxybutyric acid or "GHB" is a GABA analogue that is a natural occurring neurotransmitter and depressant drug. It is also naturally found in small amounts some alcoholic beverages alongside ethanol. GHB is the prototypical substance among a couple of GHB receptor modulators. GHB has been used as a general anesthetic and as a treatment for cataplexy, narcolepsy, and alcoholism. The sodium salt of GHB, sodium oxybate, is commonly used today for narcolepsy, sudden muscle weakness, and excessive daytime sleepiness. It is sold under the brand name Xyrem. an excitatory receptor that releases dopamine and glutamate giving GHB stimulant effects, the opposite of a depressant. But in large doses GHB activates the GABAB receptor, an inhibitory receptor in the central nervous system, which overpowers the excitatory effects, thus causing central nervous system depression. Some antipsychotics are agonists of the GHB receptor. GHB can usually be found in either as sodium, potassium, magnesium, or calcium salts. Xywav is a medication that is a mixture of all GHB salts and is used to treat the same conditions as Xyrem. Both Xywav and Xyrem are Schedule III and have a black box warning for central nervous system depressant effects (hypoventilation & bradycardia) and for their very high potential for abuse. Death from GHB overdose is usually caused by respiratory depression, seizures, or coma. GHB is used illegally as an intoxicant, an aphrodisiac, and as an athletic performance enhancer. It has also been reportedly used as a date rape drug. This caused it to be a Schedule I substance in the United States and Canada and other countries. Xyrem, which is GHB in its sodium form, is Schedule III in the United States, Canada and other countries. The GHB receptor is an excitatory G protein coupled receptor (GPCR). the mechanism is currently not known but it is believed to be due to interactions with the GABAB receptor. GHB withdrawal is very intense. Physical dependence develops quickly. It is also highly psychologically addictive. It shares some similarities with the withdrawal of gabapentinoids phenibut and baclofen due to the activation of the GABAB receptor. It features a typical depressant withdrawal syndrome that mimics alcohol withdrawal. Symptoms include delirium, tremor, anxiety, tachycardia, insomnia, hypertension, confusion, sweating, severe agitation which may require restraint, auditory and visual hallucinations and possibly death from tonic clonic seizures. Baclofen and phenibut are very effective for withdrawal and are preferred by patients over benzodiazepines for treatment of withdrawal. They are structurally related do benzodiazepines. They positively modulate the benzodiazepine site of the GABAA receptor, the chief inhibitory receptor of the central nervous system just like benzodiazepines, but a molecular level, they are structurally unrelated. Nonbenzodiazepines bind to the benzodiazepine of the GABAA receptor site to keep the chloride channel open. This causes chloride in the intercellular area to flood into the neuron. Since chloride has a negative charge it causes the neuron to rest and cease firing. This results in a relaxing and depressant effect in the central nervous system. Common nonbenzodiazepines like Zolpidem and Zopiclone are extremely effective for insomnia but carry many risks and side effects. Sleeping pills, including zopiclone, have been associated with an increased risk of death. Adverse reactions as follows: "taste disturbance (some report a metallic like taste); less commonly nausea, vomiting, dizziness, drowsiness, dry mouth, headache; rarely amnesia, confusion, depression, hallucinations, nightmares; very rarely light headedness, incoordination, paradoxical effects, and sleep walking also reported". Some users of nonbenzodiazepines have sleep walked and committed murders or have been involved in motor vehicle accidents. Unlike benzodiazepines, nonbenzodiazepines have a risk of hallucinations and sleep walking. Like benzodiazepines, they can cause anterograde amnesia. Nonbenzodiazepines should not be discontinued abruptly if taken for more than a few weeks due to the risk of rebound withdrawal effects and acute withdrawal reactions, which may resemble those seen during benzodiazepine withdrawal. Treatment usually entails gradually reducing the dosage over a period of weeks or several months depending on the individual, dosage, and length of time the drug has been taken. If this approach fails, a crossover to a benzodiazepine equivalent dose of a long acting benzodiazepine (such as chlordiazepoxide or more preferably diazepam) can be tried followed by a gradual reduction in dosage. In extreme cases and, in particular, where severe addiction and/or abuse is manifested, an inpatient detoxification may be required, with flumazenil as a possible detoxification tool.

Alpha and beta blockers (carvedilol, propranolol, atenolol, etc.) Anticholinergics (atropine, hyoscyamine, scopolamine, etc.) Anticonvulsants (topiramate, carbamazepine, lamotrigine, etc.) Antihistamines (diphenhydramine, doxylamine, promethazine, etc.) Antipsychotics (haloperidol, chlorpromazine, clozapine, etc.) Hypnotics (zolpidem, zopiclone, chloral hydrate, eszopiclone, etc.) Muscle relaxants (baclofen, phenibut, carisoprodol, cyclobenzaprine, etc.) Sedatives (gamma hydroxybutyrate, etc.)

Combining multiple depressants can be very dangerous because the central nervous system's depressive properties have been proposed to increase exponentially instead of linearly. This characteristic makes depressants a common choice for deliberate overdoses in the case of suicide. The use of alcohol or benzodiazepines along with the usual dose of heroin is often the cause of overdose deaths in opiate addicts.