Tolerance and physical<unk>  Tolerance develops rapidly to the sleep-inducing effects of benzodiazepines. The anticonvulsant and muscle-relaxant effects last for a few weeks before tolerance develops in most individuals. Tolerance results in a desensitization of GABA receptors and an increased sensitization of the excitatory neurotransmitter system, such as NMDA glutamate receptors. These changes occur as a result of the body trying to overcome the drug's effects. Other changes that occur are the reduction of the number of GABA receptors (downregulation) as well as possibly long-term changes in gene transcription coding of brain cells. The differing speed at which tolerance occurs to the therapeutic effects of benzodiazepines can be explained by the speed of changes in the range of neurotransmitter systems and subsystems that are altered by chronic benzodiazepine use. The various neurotransmitter systems and subsystems may reverse tolerance at different speeds, thus explaining the prolonged nature of some withdrawal symptoms. As a result of a physical<unk>  that develops due to tolerance, a characteristic benzodiazepine withdrawal syndrome often occurs after removal of the drug or a reduction in dosage. Changes in the expression of neuropeptides such as corticotropin-releasing hormone and neuropeptide Y may play a role in<unk> . Individuals taking daily benzodiazepine drugs have a reduced sensitivity to further additional doses of benzodiazepines. Tolerance to benzodiazepines can be demonstrated by injecting diazepam into long-term users. In normal subjects, increases in growth hormone occurs, whereas, in benzodiazepine-tolerant individuals, this effect is blunted. Animal studies have shown that repeated withdrawal from benzodiazepines leads to increasingly severe withdrawal symptoms, including an increased risk of seizures; this phenomenon is known as kindling. Kindling phenomena are well established for repeated ethanol (alcohol) withdrawal; alcohol has a very similar mechanism of tolerance and withdrawal to benzodiazepines, involving the GABA, NMDA, and AMPA receptors. The shift of benzodiazepine receptors to an inverse agonist state after chronic treatment leads the brain to be more sensitive to excitatory drugs or stimuli. Excessive glutamate activity can result in excitotoxicity, which may result in neurodegeneration. The glutamate receptor subtype NMDA is well known for its role in causing excito-neurotoxicity. The glutamate receptor subtype AMPA is believed to play an important role in neuronal kindling as well as excitotoxicity during withdrawal from alcohol as well as benzodiazepines. It is highly possible that NMDA receptors are involved in the tolerance to some effects of benzodiazepines. Animal studies have found that glutamergic changes as a result of benzodiazepine use are responsible for a delayed withdrawal syndrome, which in mice peaks 3 days after cessation of benzodiazepines. This was demonstrated by the ability to avoid the withdrawal syndrome by the administration of AMPA antagonists. It is believed that different glutamate subreceptors, e.g., NMDA and AMPA, are responsible for different stages/time points of the withdrawal syndrome. NMDA receptors are upregulated in the brain as a result of benzodiazepine tolerance. AMPA receptors are also involved in benzodiazepine tolerance and withdrawal. A decrease in benzodiazepine binding sites in the brain may also occur as part of benzodiazepine tolerance. Cross tolerance Benzodiazepines share a similar mechanism of action with various sedative compounds that act by enhancing the GABAA receptor. Cross tolerance means that one drug will alleviate the withdrawal effects of another. It also means that tolerance of one drug will result in tolerance of another similarly-acting drug. Benzodiazepines are often used for this reason to detoxify alcohol-dependent patients and can have life-saving properties in preventing or treating severe life-threatening withdrawal syndromes from alcohol, such as delirium tremens. However, although benzodiazepines can be very useful in the acute detoxification of alcoholics, benzodiazepines in themselves act as positive reinforcers in alcoholics, by increasing the desire for alcohol. Low doses of benzodiazepines were found to significantly increase the level of alcohol consumed in alcoholics. Alcoholics dependent on benzodiazepines should not be abruptly withdrawn but be very slowly withdrawn from benzodiazepines, as over-rapid withdrawal is likely to produce severe anxiety or panic, which is well known for being a relapse risk factor in recovering alcoholics. There is cross tolerance between alcohol, the benzodiazepines, the barbiturates, the nonbenzodiazepine drugs, and corticosteroids, which all act by enhancing the GABAA receptor's function via modulating the chloride ion channel function of the GABAA receptor. Neuroactive steroids, e.g., progesterone and its active metabolite allopregnanolone, are positive modulators of the GABAA receptor and are cross tolerant with benzodiazepines. The active metabolite of progesterone has been found to enhance the binding of benzodiazepines to the benzodiazepine binding sites on the GABAA receptor. The cross-tolerance between GABAA receptor positive modulators, including benzodiazepines, occurs because of the similar mechanism of action and the subunit changes that occur from chronic use from one or more of these compounds in expressed receptor isoforms. Abrupt withdrawal from any of these compounds, e.g., barbiturates, benzodiazepines, alcohol, corticosteroids, neuroactive steroids, and nonbenzodiazepines, precipitate similar withdrawal effects characterized by central nervous system hyper-excitability, resulting in symptoms such as increased seizure susceptibility and anxiety. While many of the neuroactive steroids do not produce full tolerance to their therapeutic effects, cross-tolerance to benzodiazepines still occurs as had been demonstrated between the neuroactive steroid ganaxolone and diazepam. Alterations of levels of neuroactive steroids in the body during the menstrual cycle, menopause, pregnancy, and stressful circumstances can lead to a reduction in the effectiveness of benzodiazepines and a reduced therapeutic effect. During withdrawal of neuroactive steroids, benzodiazepines become less effective. Physiology of withdrawal Withdrawal symptoms are a normal response in individuals having chronically used benzodiazepines, and an adverse effect and result of drug tolerance. Symptoms typically emerge when dosage of the drug is reduced. GABA is the second-most-common neurotransmitter in the central nervous system (the most common being glutamate) and by far the most abundant inhibitory neurotransmitter; roughly one-quarter to one-third of synapses use GABA. The use of benzodiazepines has a profound effect on almost every aspect of brain and body function, either directly or indirectly. Benzodiazepines cause a decrease in norepinephrine (noradrenaline), serotonin, acetylcholine, and dopamine. These neurotransmitters are needed for normal memory, mood, muscle tone and coordination, emotional responses, endocrine gland secretions, heart rate, and blood pressure control. With chronic benzodiazepine use, tolerance develops rapidly to most of its effects, so that, when benzodiazepines are withdrawn, various neurotransmitter systems go into overdrive due to the lack of inhibitory GABA-ergic activity. Withdrawal symptoms then emerge as a result, and persist until the nervous system physically reverses the adaptions (physical<unk>  that have occurred in the CNS. Withdrawal symptoms typically consist of a mirror image of the drug's effects: Sedative effects and suppression of REM and SWS stages of sleep can be replaced by insomnia, nightmares, and hypnogogic hallucinations; its antianxiety effects are replaced with anxiety and panic; muscle-relaxant effects are replaced with muscular spasms or cramps; and anticonvulsant effects are replaced with seizures, especially in cold turkey or overly-rapid withdrawal. Benzodiazepine withdrawal represents in part excitotoxicity to brain neurons. Rebound activity of the hypothalamic-pituitary-adrenocortical axis also plays an important role in the severity of benzodiazepine withdrawal. Tolerance and the resultant withdrawal syndrome may be due to alterations in gene expression, which results in long-term changes in the function of the GABAergic neuronal system. During withdrawal from full or partial agonists, changes occur in benzodiazepine receptor with upregulation of some receptor subtypes and downregulation of other receptor subtypes. Withdrawal Long-term use of benzodiazepines leads to increasing physical and mental health problems, and as a result, discontinuation is recommended for many long-term users. The withdrawal syndrome from benzodiazepines can range from a mild and short-lasting syndrome to a prolonged and severe syndrome. Withdrawal symptoms can lead to continued use of benzodiazepines for many years, long after the original reason for taking benzodiazepines has passed. Many patients know that the benzodiazepines no longer work for them but are unable to discontinue benzodiazepines because of withdrawal symptoms. Withdrawal symptoms can emerge despite slow reduction but can be reduced by a slower rate of withdrawal. As a result, withdrawal rates have been recommended to be customized to each individual patient. The time needed to withdrawal can vary from a couple of months to a year or more and often depends on length of use, dosage taken, lifestyle, health, and social and environmental stress factors. Diazepam is often recommended due to its long elimination half-life and also because of its availability in low potency doses. The non-benzodiazepine Z drugs such as zolpidem, zaleplon, and zopiclone should not be used as a replacement for benzodiazepines, as they have a similar mechanism of action and can induce a similar<unk> . The pharmacological mechanism of benzodiazepine tolerance and<unk>  is the internalization (removal) of receptor site in the brain and changes in gene transcription codes in the brain. With long-term use and during withdrawal of benzodiazepines, treatment-emergent depression and emotional blunting may emerge and sometimes also suicidal ideation. There is evidence that the higher the dose used the more likely it is benzodiazepine use will induce these feelings. Reducing the dose or discontinuing benzodiazepines may be indicated in such cases. Withdrawal symptoms can persist for quite some time
Benzodiazepine dependence
Opioid withdrawal
Amphetamine dependence
Drug withdrawal
Nicotine withdrawal
Cocaine dependence
Benzodiazepine withdrawal syndrome
Benzodiazepine use disorder