(British Approved Name Modified, US Adopted Name, rINNM)
INNs in main languages (French, Latin, Russian, and Spanish):
Note. The following terms have been used as ‘street names’ (see p.vi) or slang names for various forms of zolpidem tartrate: Sleepeasy; Tic-Tacs.
Pharmacopoeias. In Europe.
European Pharmacopoeia, 6th ed. (Zolpidem Tartrate). A white or almost white hygroscopic crystalline powder. Slightly soluble in water practically insoluble in dichloromethane sparingly soluble in methyl alcohol. Store in airtight containers. Protect from light.
Dependence and Withdrawal
As for Diazepam.
Withdrawal symptoms. A 37-year-old man, who increased his dose from 10 mg to 130 mg daily over 2 months, had a generalised tonic-clonic seizure after zolpidem was abruptly stopped. The patient recovered after being started on a benzodiazepine dosage tapering programme. Symptoms attributed to daytime abstinence after excessive night-time doses have been reported in 2 patients and included anxiety, tremor, sweating, nausea, gastric and abdominal pain, swallowing difficulties, tachycardia, and tachypnoea. The patients had increased their doses because of the development of tolerance to the hypnotic effect but had begun to experience muscle twitches and myoclonic jerks.
Adverse Effects, Treatment, and Precautions
As for Diazepam.
Treatment of overdose is largely supportive. Activated charcoal may be given orally within one hour of ingestion of 100 mg zolpidem or more by adults, or more than 5 mg by children. Alternatively, gastric lavage may be considered in adults if they present within 1 hour of a potentially life-threatening overdose. Fluma-zenil may be considered in cases of severe CNS depression (see also Overdosage, below).
Abuse. Zolpidem abuse has been reported effects noted include a paradoxical stimulant effect when taking large doses of zolpidem. Tolerance may also develop. Intravenous abuse has also been reported. See also under Dependence and Withdrawal, above.
Breast feeding. No adverse effects have been seen in breastfed infants whose mothers were receiving zolpidem, and the American Academy of Pediatrics considers that it is therefore usually compatible with breast feeding.
In 5 women given a 20-mg dose of zolpidem, the amount of drug excreted in breast milk after 3 hours ranged between 0.76 and 3.88 micrograms, which represented 0.004 to 0.019% of the dose. No detectable (below 0.5 nanograms/mL) zolpidem was found in subsequent milk samples.
Effects on the liver. Hepatitis developed on 2 separate occasions in a 53-year-old woman after the use of zolpidem for insomnia.
Effects on mental function. Psychotic reactions, which may not subsequently be recalled, have been reported in patients taking therapeutic doses of zolpidem. Somnambulism has also been reported with zolpidem. Other complex sleep-related behaviours, such as eating or driving while asleep, have been reported with zaleplon, zolpidem, and zopiclone. Such behaviour is more likely to occur when these drugs are taken with alcohol or other CNS depressants, or when taken in doses exceeding the recommended maximum. It is not clear if there are differences in risk with individual drugs however, as a precautionary measure, the FDA had requested for labelling changes that highlight these adverse effects to be made to all hypnotics marketed in the USA.
Hypersensitivity. Rare cases of angioedema involving the tongue, glottis, or larynx have been reported after the first or subsequent doses of hypnotics such as eszopiclone, zaleplon, zolpidem, and zopiclone additional symptoms suggestive of anaphylaxis have also developed in some patients.
Overdosage. A retrospective analysis of 344 cases of acute overdosage with zolpidem reported to the Paris Poison Center and the manufacturers Synthelabo has been published. The ingested dose, where known, ranged from 10 to 1400 mg, and the most common adverse effect was drowsiness (in 89 patients). Other adverse effects probably associated with the overdosage included coma in 4 patients and vomiting in 7. Recovery was usually rapid when overdosage involved only zolpidem. It was recommended that patients who had ingested more than 100 mg of zolpidem should undergo gastric lavage and should be monitored for at least 12 hours (see also above). Although it has been shown that flumazenil can effectively antagonise the CNS effects of zolpidem the authors of this analysis found that in general it was not required.
As for Diazepam.
Antidepressants. A 16-year-old girl who had been taking par-oxetine 20 mg daily for 3 days began to hallucinate and became disorientated one hour after taking zolpidem 10 mg at night. The delirium cleared spontaneously 4 hours later without treatment. When questioned, at least one other of the author’s patients receiving this combination reported transient visual hallucinations. Other isolated cases of visual hallucinations have been reported in patients taking zolpidem with antidepressants including bupropion, desipramine, fluoxetine, sertraline, and venlafaxine.
Antiepileptics. A 47-year-old man with a history of bipolar disorder, who was receiving citalopram and zolpidem, had episodes of somnambulism after he was also given valproic acid‘for treatment of manic symptoms. The episodes stopped on withdrawal of valproic acid and returned on rechallenge. An interaction between zolpidem and valproic acid was suspected (but somnambulism has also been associated with zolpidem alone, see Effects on Mental Function, above).
For the suggestion that carbamazepine and phenytoin may interact with zolpidem, see Rifampicin, below.
Antifungals. Use of‘ketoconazole with zolpidem has resulted in increased plasma concentrations, and an enhanced sedative effect, of zolpidem, albeit only modest. The use of zolpidem with fluconazole or itraconazole has resulted in small, non-significant changes in the pharmacokinetics and sedative effects of zolpidem.
Antivirals. HIV-protease inhibitors such as ritonavir may increase plasma concentrations of zolpidem with a risk of extreme sedation and respiratory depression use together is possible provided the patient is carefully monitored for excessive sedative effects.
Rifampicin. Rifampicin reduced the hypnotic effect of zolpidem in a study in 8 healthy female subjects. The area under the curve for zolpidem was reduced by 73% after rifampicin and the peak plasma concentration by 58%. The elimination half-life of zolpidem was reduced from 2.5 to 1.6 hours. Similar effects could be expected with other potent inducers of the cytochrome P450 isoenzyme CYP3A4 such as carbamazepine and phenytoin.
Zolpidem is rapidly absorbed from the gastrointestinal tract after oral doses, peak plasma concentrations being reached within 3 hours. Zolpidem undergoes first-pass metabolism and an absolute bioavailability of about 70% has been reported. Zolpidem has an elimination half-life of about 2.5 hours and is about 92% bound to plasma proteins. It is metabolised primarily by the cytochrome P450 isoenzyme CYP3A4 the inactive metabolites of zolpidem are excreted in the urine and faeces. Zolpidem is distributed into breast milk.
Uses and Administration
Zolpidem tartrate is an imidazopyridine that is reported to have similar sedative properties to the benzodiazepines (see Diazepam), but minimal anxiolytic, muscle relaxant, and anticonvulsant properties. It has a rapid onset and short duration of action, and is used as a hypnotic in the short-term management of insomnia. The usual oral dose is 10 mg taken immediately before retiring. In elderly or debilitated patients, treatment should be limited to a dose of 5 mg at night. Doses should also be reduced in patients with hepatic impairment, see below. A modified-release formulation of zolpidem tartrate is also available.
Administration in hepatic impairment. In patients with hepatic impairment, treatment with immediate-release formulations of zolpidem tartrate should be started with a dose of 5 mg at night the dose may be increased to lOmg, if necessary, in those under 65 years. UK licensed product information contra-indicates the use of zolpidem in patients with severe impairment.
Catatonia. Anecdotal reports suggesting that zolpidem may be a useful test in the diagnosis of catatonia.
Insomnia. Zolpidem is an imidazopyridine with strong sedative actions, but only minor anxiolytic, muscle relaxant, or anticonvulsant properties. Some degree of amnesia has been reported. Zolpidem appears to act by binding to the benzodiazepine receptor component of the GABA receptor complex. It has, however, a selective affinity for the subtype of benzodiazepine receptors prevalent in the cerebellum (BZ1 – or ω1-receptors) as opposed to those more commonly found in the spinal cord (BZ2- or ω2-re-ceptors) or in the peripheral tissues (BZ3- or ω3-receptors). Zolpidem has a rapid onset and short duration of hypnotic action and at usual doses decreases time to sleep onset and increases duration of sleep with little apparent effect on sleep stages (see Insomnia). Reviews agree that clinical studies have shown zolpidem to have hypnotic activity superior to placebo and generally similar to comparative benzodiazepines. Although it does not appear to produce rebound insomnia to any great extent, there appears to be little evidence that zolpidem offers any advantage over short-acting benzodiazepines in terms of residual effects the next day, or its potential to induce tolerance or withdrawal symptoms or dependence (see also under Dependence and Withdrawal, above).
Parkinsonism. Although preliminary findings in 10 patients suggested that zolpidem might improve symptoms of Parkinson’s disease concern has been expressed over the risk of falls associated with zolpidem-induced drowsiness and the serious consequences for these patients. Benefit has also been reported in the treatment of antipsychotic-induced parkinsonism in one patient with symptoms of repetitive persistent gross tremors of the hands.
Permanent vegetative state. Zolpidem in a single dose of 10 mg has produced temporary arousal in 3 patients thought to be in permanent vegetative state. Effects lasted for about 4 hours.
Argentina: Balidorm Dormilan Durnit Nocte Somit Sumenan Zolodorm
Australia: Dormizol Somidem Stildem Stilnox Zolpibell
Austria: Ivadal Mondeal Zoldem Zolpidohexal
Brazil: Lioram Stilnox
Chile: Adormix Damixan Dormilam Dormosol Somnil Somnipron Somno Sucedal
Czech Republic: Eanox Hypnogen Stilnoct Stilnox Zolpimerck Zolpinox Zolsana Zonadin
Denmark: Eanox Nimadorm Stilnoct Zonoct
Finland: Somnor Stella Stilnoct
Germany: Bikalm Stilnox Zodormdura Zoldem Zolpi-Lich Zolpi-Q Zolpinox
Greece: Alespan Hypnoforin Stilnox
Hong Kong: Stilnox Stilpidem
Hungary: Ambien Hypnogen Pidezol Sanval Stilnox
India: Ambiz Sove Zleep Zoldem
Indonesia: Stilnox Zolmia
Ireland: Nytamel Stilnoct Zoldem Zolnod
Israel: Stilnox Zodorm
Italy: Niotal Nottem Stilnox
Malaysia: Sobrium Somidem Stilnox
Mexico: Nocte Stilnox
The Netherlands: Stilnoct Zolpidol
Philippines: Stilnox Ziohex
Poland: Hypnogen Nasen Polsen Sanval Stilnox Xenix Zolpic Zolpi
Germany: Zolsana Zoratio
Portugal: Cymerion Stilnox
Russia: Hypnogen Nitrest Sanval Snovitel
South Africa: Ivedal Noxidem Stilnox Zolnoxs Zolpihexal
Spain: Dalparan Stilnox
Switzerland: Sedovalin Stilnox Zoldorm Zolpi-Med
USA: Ambien Tovalt
Venezuela: Atrimon Stilnox Zolpidex