Zolpidem

Zolpidem (Ambien, Stilnox) is a prescription medication used for the short-term treatment of insomnia, as well as some brain disorders. It is a short-acting nonbenzodiazepine hypnotic of the imidazopyridine class that potentiates gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter, by binding to GABAA receptors at the same location as benzodiazepines. It works quickly (usually within 15 minutes) and has a short half-life (2–3 hours).

Zolpidem has not adequately demonstrated effectiveness in maintaining sleep; however, it is effective in initiating sleep. Its hypnotic effects are similar to those of the benzodiazepine class of drugs, but it is molecularly distinct from the classical benzodiazepine molecule and is classified as an imidazopyridine. Flumazenil, a benzodiazepine receptor antagonist, which is used for benzodiazepine overdose, can also reverse zolpidem's sedative/hypnotic and memory impairing effects.

As an anticonvulsant and muscle relaxant, the beneficial effects start to emerge at 10 and 20 times the dose required for sedation, respectively. For that reason, it has never been approved for either muscle relaxation or seizure prevention. Such drastically increased doses are more inclined to induce one or more negative side-effects, including hallucinations and amnesia.

Zolpidem is one of the most common GABA-potentiating sleeping medications prescribed in the Netherlands, with a total of 582,660 prescriptions dispensed in 2008. The patent in the United States on zolpidem was held by the French pharmaceutical corporation Sanofi-Aventis. On April 23, 2007 the U.S. Food and Drug Administration (FDA) approved 13 generic versions of zolpidem tartrate. Zolpidem is available from several generic manufacturers in the UK, as a generic from Sandoz in South Africa, TEVA in Israel, as well as from other manufacturers such as Ratiopharm (Germany).

Medical uses
Zolpidem is used for short-term (usually about two to six weeks) treatment of insomnia. It has been studied for nightly use up to six months in a single-blind trial published in 1991, an open-label study lasting 180 days published in 1992 (with continued efficacy in patients who had kept taking it as of 180 days after the end of the trial), and in an open-label trial lasting 179 days published in 1993. Zolpidem has not proven effective in maintaining sleep and is more used for sleep initiation problems.

The United States Air Force uses zolpidem as one of the hypnotics approved as "no-go pills" to help aviators and special duty personnel sleep in support of mission readiness (the other hypnotics used are temazepam and triazolam during war time). "Ground tests" are required prior to authorization issued to use the medication in an operational situation.

Adverse effects
Side-effects at any dose may include:
 * Nausea
 * Vomiting
 * Anterograde amnesia
 * Hallucinations, through all physical senses, of varying intensity
 * Delusions
 * Altered thought patterns
 * Ataxia or poor motor coordination, difficulty maintaining balance
 * Euphoria and/or dysphoria
 * Increased appetite
 * Increased Libido or decreased libido/destrudo
 * Amnesia
 * Impaired judgment and reasoning
 * Uninhibited extroversion in social or interpersonal settings
 * Increased impulsivity
 * When stopped, rebound insomnia may occur
 * Headaches
 * Short term memory loss

Some users have reported unexplained sleepwalking while using zolpidem, and a few have reported driving, binge eating, sleep talking, and performing other daily tasks while sleeping. Research by Australia's National Prescribing Service found that these events occur mostly after the first dosage taken or within a few days of starting therapy. Rare reports of sexual parasomnia episodes related to zolpidem intake have also been reported. The sleepwalker can sometimes perform these tasks as normally as they might if they were awake. They can sometimes carry on complex conversations and respond appropriately to questions or statements so much so that the observer may believe the sleepwalker to be awake. This is similar to, but unlike, typical sleep talking, which can usually be identified easily and is characterised by incoherent speech that often has no relevance to the situation or that is so disorganised as to be completely unintelligible. Those under the influence of this medication may seem fully aware of their environment even though they are still asleep. This can bring about concerns for the safety of the sleepwalker and others. These side-effects may be related to the mechanism that also causes zolpidem to produce its hypnotic properties. It is unclear whether the drug is responsible for the behavior, but a class-action lawsuit was filed against Sanofi-Aventis in March 2006 on behalf of those that reported symptoms. It is possible some users believe they were asleep during events they interacted in because they do not remember the events, due to the short-term memory loss and anterograde amnesia side-effects.

Residual 'hangover' effects such as sleepiness, impaired psychomotor and cognitive after nighttime administration may persist into the next day, which may impair the ability of users to drive safely, increase risks of falls and hip fractures.

The Sydney Morning Herald in Australia reported in 2007 that a man who fell 30 meters to his death from a high-rise unit balcony may have been sleepwalking under the influence of Stilnox. The coverage prompted over 40 readers to contact the newspaper with their own accounts of Stilnox-related automatism, and, the drug was under review by the Adverse Drug Reactions Advisory Committee.

In February 2008, the Australian Therapeutic Goods Administration attached a Black Box Warning to zolpidem, stating that "Zolpidem may be associated with potentially dangerous complex sleep-related behaviours that may include sleep walking, sleep driving, and other bizarre behaviours. Zolpidem is not to be taken with alcohol. Caution is needed with other CNS depressant drugs.  Limit use to four weeks maximum under close medical supervision." This report received widespread media coverage after the death of Australian student Mairead Costigan, who fell 20m from the Sydney Harbour Bridge while under the influence of Stilnox.

Tolerance, dependence, and withdrawal
A review medical publication found that long term use of zolpidem is associated with drug tolerance, drug dependence, rebound insomnia and CNS related adverse effects. It was recommended that zolpidem be used for short periods of time using the lowest effective dose. Zolpidem 10 mg is effective in treating insomnia when used intermittently no fewer than 3 and no more than 5 pills per week for a period of 12 weeks. 15-mg zolpidem dosage provided no clinical advantage over the 10-mg zolpidem dosage.

Non-pharmacological treatment options (e.g. cognitive behavioral therapy for insomnia) however, were found to have sustained improvements in sleep quality. Animal studies of the tolerance inducing properties have shown that in rodents zolpidem has less tolerance-producing potential than benzodiazepines, but in primates the tolerance-producing potential of zolpidem was the same as that of benzodiazepines. Tolerance can develop in some people to the effects of zolpidem in just a few weeks. Abrupt withdrawal of zolpidem may cause delirium, seizures, or other severe effects, especially if used for prolonged periods and at high dosages.

When drug tolerance and physical dependence to zolpidem has developed, treatment usually entails a gradual dose reduction over a period of months in order to minimise withdrawal symptoms that can resemble those seen during benzodiazepine withdrawal. Failing that, an alternative method that may be necessary for some patients is a switch to a benzodiazepine equivalent dose of a longer-acting benzodiazepine drug such as diazepam or chlordiazepoxide followed by a gradual reduction in dosage of the long-acting benzodiazepine. Sometimes for difficult-to-treat patients, an inpatient flumazenil rapid detoxification program can be used to detox from a zolpidem drug dependence or addiction.

Alcohol has cross tolerance with GABAa receptor positive modulators such as the benzodiazepines and the nonbenzodiazepine drugs. For this reason, alcoholics or recovering alcoholics may be at increased risk of physical dependency on zolpidem. Also, alcoholics and drug abusers may be at increased risk of abusing and or becoming psychologically dependent on zolpidem. Zolpidem should be avoided in those with a history of Alcoholism, drug misuse, physical dependency, or psychological dependency on sedative-hypnotic drugs.

Overdose
An overdose of zolpidem may cause excessive sedation, pin-point pupils, depressed respiratory function, which may progress to coma and possibly death. Zolpidem combined with alcohol, opiates, or other CNS depressants may be even more likely to lead to fatal overdoses. Zolpidem overdosage can be treated with the benzodiazepine receptor antagonist flumazenil, which displaces zolpidem from its binding site the benzodiazepine receptor and, therefore, rapidly reverses the effects of zolpidem.

Detection in body fluids
Zolpidem may be quantitated in blood or plasma to confirm a diagnosis of poisoning in hospitalized patients, provide evidence in an impaired driving arrest, or to assist in a medicolegal death investigation. Blood or plasma zolpidem concentrations are usually in a range of 30–300 μg/L in persons receiving the drug therapeutically, 100–700 μg/L in those arrested for impaired driving, and 1000–7000 μg/L in victims of acute overdosage. Analytical techniques, in general, involve gas or liquid chromatography.

Driving
Use of zolpidem may impair driving skills with a resultant increased risk of road traffic accidents. This adverse effect is not unique to zolpidem but also occurs with other hypnotic drugs. Caution should be exercised by motor vehicle drivers.

Elderly
The elderly are more sensitive to the effects of hypnotics including zolpidem. Zolpidem causes an increased risk of falls and may induce cognitive adverse effects.

An extensive review of the medical literature regarding the management of insomnia and the elderly found that there is considerable evidence of the effectiveness and durability of non-drug treatments for insomnia in adults of all ages and that these interventions are underutilized. Compared with the benzodiazepines, the nonbenzodiazepine (including zolpidem) sedative-hypnotics appeared to offer few, if any, significant clinical advantages in efficacy or tolerability in elderly persons. It was found that newer agents with novel mechanisms of action and improved safety profiles, such as the melatonin agonists, hold promise for the management of chronic insomnia in elderly people. Long-term use of sedative-hypnotics for insomnia lacks an evidence base and has traditionally been discouraged for reasons that include concerns about such potential adverse drug effects as cognitive impairment (anterograde amnesia), daytime sedation, motor incoordination, and increased risk of motor vehicle accidents and falls. In addition, the effectiveness and safety of long-term use of these agents remain to be determined. It was concluded that more research is needed to evaluate the long-term effects of treatment and the most appropriate management strategy for elderly persons with chronic insomnia.

Gastroesophageal reflux disease
Taking zolpidem dramatically increases the duration of gastroesophageal reflux events, as patients are less likely to become aroused from the event and initiate a swallowing reflex. Patients suffering from gastroesophageal reflux disease had reflux events measured to be significantly longer when taking zolpidem than on placebo. (The same trend was found for reflux events in patients without GERD). This is assumed to be due to suppression of arousal during the reflux event, which would normally result in a swallowing reflex to clear gastric acid from the esophagus. Patients with GERD who take zolpidem thus experience significantly higher esophageal exposure to gastric acid, which increases the likelihood of developing esophageal cancer.

Pregnancy
Zolpidem has been assigned to pregnancy category C by the FDA. Animal studies have revealed evidence of incomplete ossification and increased postimplantation fetal loss at doses greater than seven times the maximum recommended human dose or higher; however, teratogenicity was not observed at any dose level. There are no controlled data in human pregnancy. In one case report, zolpidem was found in cord blood at delivery. Zolpidem is only recommended for use during pregnancy when benefit outweighs risk.

Mechanism of action
Due to its selective binding, Zolpidem has very weak anxiolytic, myorelaxant, and anticonvulsant properties but very strong hypnotic properties. Zolpidem binds with high affinity and acts as a full agonist at the α1-containing GABAA receptors, about 10-fold lower affinity for those containing the α2- and α3- GABAA receptor subunits, and with no appreciable affinity for α5 subunit-containing receptors. ω1 type GABAA receptors are the α1-containing GABAA receptors and ω2 GABAA receptors are the α2-, α3-, α4-, α5-, and α6-containing GABAA receptors. ω1 GABAA receptors are found primarily in the brain, whereas ω2 receptors are found primarily in the spine. Thus, zolpidem has a preferential binding for the GABAA-benzodiazepine receptor complex in the brain but a low affinity for the GABAA-benzodiazepine receptor complex in the spine.

Like the vast majority of benzodiazepine-like molecules, zolpidem has no affinity for α4 and α6 subunit-containing receptors. Zolpidem positively modulates GABAA receptors, it is presumed by increasing the GABAA receptor complexes apparent affinity for GABA, without affecting desensitization or peak current. Zolpidem increases slow wave sleep and caused no effect on stage 2 sleep in laboratory tests.

A meta-analysis of the randomised controlled clinical trials that compared benzodiazepines against Z-drugs such as zolpidem has shown that there are few consistent differences between zolpidem and benzodiazepines in terms of sleep onset latency, total sleep duration, number of awakenings, quality of sleep, adverse events, tolerance, rebound insomnia, and daytime alertness.

Drug-drug interactions
Notable drug-drug interactions with the pharmacokinetics of zolpidem include the following drugs chlorpromazine, fluconazole, imipramine, itraconazole, ketoconazole, rifampicin, ritonavir. Interactions with carbamazepine and phenytoin can be expected based on their metabolic pathways but have not yet been studied. There does not appear to be any interaction between zolpidem and cimetidine and ranitidine. http://www.ncbi.nlm.nih.gov/pubmed/3253224

Recreational use
Zolpidem has a potential for either medical misuse when the drug is continued long term without or against medical advice, or recreational use when the drug is taken to achieve a high. The transition from medical use of zolpidem to high-dose addiction or drug dependence can occur when used without a doctor's recommendation to continue using it, when physiological drug tolerance leads to higher doses than the usual 5 mg or 10 mg, when consumed through insufflation or injection, or when taken for purposes other than as a sleep aid. Misuse is more prevalent in those that have been dependent on other drugs in the past, but tolerance and drug dependence can still sometimes occur in those without a history of drug dependence. Chronic users of high doses are more likely to have a severe physical dependence on the drug, which may cause severe withdrawal symptoms including seizures if abrupt withdrawal from zolpidem occurs.

As is the case with many prescription sedative/hypnotic drugs, it is sometimes used by stimulant users to "come down" after the use of stimulants such as amphetamines, methamphetamine, cocaine, and MDMA (ecstasy).

One case history report involved a woman detoxing off a high dose of zolpidem experiencing a generalized seizure, with clinical withdrawal and dependence effects reported to be similar to the benzodiazepine withdrawal syndrome.

The recreational-misuse of zolpidem is becoming more common in U.S.A, Canada, and the UK. Sold on the street as Abee'ss, Amee's or Amb'zz. Recreational users claim that "fighting" the effects of the drug by forcing themselves to stay awake will sometimes cause vivid visuals and a body high. Some users report decreased anxiety, mild euphoria, perceptual changes, visual distortions, and hallucinations.

Zolpidem has been used on victims of sexual assault.

Zolpidem and other sedative hypnotic drugs are detected frequently in cases of people suspected of driving under the influence of drugs. Other drugs including the benzodiazepines and zopiclone are also found in high numbers of suspected drugged drivers. Many drivers have blood levels far exceeding the therapeutic dose range suggesting a high degree of excessive-use potential for benzodiazepines, zolpidem and zopiclone. U.S. Congressman Patrick J. Kennedy says that he was using Zolpidem (Ambien) and Phenergan when caught driving erratically at 3AM. "I simply do not remember getting out of bed, being pulled over by the police, or being cited for three driving infractions," Kennedy said.

Partially due to recreation potential, Zolpidem, along with the other benzodiazapine-like "Z-drugs", is a Schedule IV Controlled Substance in the USA, according to the Controlled Substances Act.

Brand names
Trade names of zolpidem include: Adormix, Ambien, Ambien CR, Edluar, Zolpimist, Damixan, Hypnogen, Ivedal, Lioran, Myslee, Nasen, Nytamel, Sanval, Somidem, Somit, Stilnoct, Stilnox, Stilnox CR, Sucedal, Zodorm, Zoldem, Zolnod, Zolnox (in South Africa), Zolpihexal and Zolsana.

Research
Zolpidem may provide short-lasting but effective improvement in symptoms of aphasia present in some survivors of stroke. The mechanism for improvement in these cases remains unexplained and is the focus of current research by several groups, to explain how a drug which acts as a hypnotic-sedative in people with normal brain function, can paradoxically increase speech ability in people recovering from severe brain injury. Use of zolpidem for this application remains experimental at this time, and is not officially approved by any pharmaceutical manufacturers of zolpidem or medical regulatory agencies worldwide.