Product Description
Temazepam
(brand names Restoril and Normison, among others) is an intermediate-acting 3-hydroxy hypnotic of the benzodiazepine class of psychoactive drugs. Temazepam is approved for the short-term treatment of insomnia. In addition, temazepam has anxiolytic (anti-anxiety), anticonvulsant, and skeletal muscle relaxant properties.
History
Temazepam was first synthesized in 1964, but it first came into use in 1969 when its ability to counter insomnia was realized.By the late 1980s, temazepam was one of the most popular and widely prescribed hypnotics on the market and it became one of the most widely prescribed drugs.
Indications
Temazepam is a hypnotic agent. In sleep laboratory studies, temazepam significantly decreased the number of nightly awakeningsbut has the drawback of distorting the normal sleep pattern.
Temazepam is officially indicated for severe insomnia and other severe or disabling sleep disorders. The prescribing guidelines in the UK limit the prescribing of hypnotics to two-to-four weeks due to concerns of tolerance and dependence.
The United States Air Force uses temazepam as one of the hypnotics approved as "no-go pills" to help aviators and special duty personnel sleep in support of mission readiness. "Ground tests" are required prior to authorization being issued to use the medication in an operational situation.[citation needed]
Contraindications
Use of temazepam should be avoided, when possible, in individuals with the following conditions:
Ataxia (gross lack of coordination of muscle movements)
Severe hypoventilation
Acute narrow-angle glaucoma
Severe hepatic deficiencies (hepatitis and liver cirrhosis decrease elimination by a factor of 2)
Severe renal deficiencies (e.g. patients on dialysis)
Sleep apnea[8]
Severe depression, particularly when accompanied by suicidal tendencies
Acute intoxication with alcohol, narcotics, or other psychoactive substances
Myasthenia gravis (autoimmune disorder causing muscle weakness)
Hypersensitivity or allergy to any drug in the benzodiazepine class
Special caution needed
Temazepam should not be used in pregnancy, as it may cause harm to the fetus. The safety and effectiveness of temazepam has not been established in children; therefore temazepam should generally not be given to individuals under 18 years of age, and should not be used at all in children under 6 months old. Benzodiazepines also require special caution if used in the elderly, alcohol or drug-dependent individuals and individuals with comorbid psychiatric disorders.
Temazepam, similar to other benzodiazepines and nonbenzodiazepine hypnotic drugs causes impairments in body balance and standing steadiness in individuals who wake up at night or the next morning. Falls and hip fractures are frequently reported. The combination with alcohol increases these impairments. Partial, but incomplete tolerance develops to these impairments.The smallest possible effective dose should be used in elderly or very ill patients, as there is a risk of apnea and/or cardiac arrest. This risk is increased when temazepam is given concomitantly with other drugs that depress the central nervous system.
Patients at a high risk for abuse and dependence
Because benzodiazepines can be abused and lead to dependence, their use should be avoided in people in certain particularly high risk groups. High risk groups include people with a history of alcohol or drug abuse or dependence, emotionally unstable patients, people with severe personality disorders (such as Borderline Personality Disorder). If temazepam is indeed prescribed to people in these groups, they should generally be monitored very closely for signs of abuse and development of dependence.
Adverse effects
Common
Side effects typical of hypnotic benzodiazepines are related to CNS depression, and include somnolence, dizziness, fatigue, ataxia, headache, lethargy, impairment of memory and learning, longer reaction time and impairment of motor functions (including coordination problems),slurred speech, decreased physical performance, numbed emotions, reduced alertness, muscle weakness, blurred vision (in higher doses), and inattention. Euphoria was rarely reported with the use of temazepam. According to the FDA, temazepam had an incidence of euphoria of 1.5%, much more rarely reported than headaches and diarrhea.Anterograde amnesia may also develop, as may respiratory depression in higher doses.
Less common
Hyperhydrosis, hypotension, burning eyes, changes in libido, hallucinations, faintness, nystagmus, vomiting, pruritus, gastrointestinal disturbances, nightmares, palpitation and paradoxical reactions including restlessness, aggression, violence, overstimulation and agitation have been reported, but are rare (less than 0.5%).
Before taking temazepam, one should ensure that at least 8 hours are available to dedicate to sleep. Failing to do so can increase the side effects of the drug.
The use of this drug in combination with alcohol potentiates the side effects, and can lead to toxicity and death.
Though rare, residual "hangover" effects after nighttime administration of temazepam such as sleepiness, impaired psychomotor and cognitive functions may persist into the next day, which may impair the ability of users to drive safely or may increase the risks of falls and hip fractures.
Tolerance and physical dependence
See also: benzodiazepine withdrawal syndrome
Tolerance
Chronic or excessive use of temazepam may cause drug tolerance, which can develop rapidly,so this drug is therefore not recommended for long-term use.In 1979 the Institute of Medicine (USA) and the National Institute on Drug Abuse stated that most hypnotics lose their sleep-inducing properties after about 3 to 14 days.In use longer than 1–2 weeks, tolerance will frequently develop towards the ability of temazepam to maintain sleep, so that the drug loses effectiveness.Some studies have observed tolerance to temazepam after as little as one week's use.Another study examined the short-term effects of the accumulation of temazepam over 7 days in elderly inpatients, and found that little tolerance developed during the accumulation of the drug.Other studies examined the use of temazepam over six days and saw no evidence of tolerance.A study in 11 young male subjects showed that significant tolerance occurs to temazepam's thermoregulatory effects and sleep inducing properties after 1 week of use of 30 mg temazepam. Body temperature is well correlated with the sleep inducing or insomnia promoting properties of drugs.
In one study the drug sensitivity of people who had used temazepam for 1–20 years was no different from that of controls.An additional study, in which at least one of the authors is employed by multiple drug companies, examined the efficacy of temazepam treatment on chronic insomnia over three months and saw no drug tolerance, with the authors even suggesting that the drug might become more effective over time.
Establishing continued efficacy beyond a few weeks can be complicated by the difficulty in distinguishing between the return of the original insomnia complaint and withdrawal or rebound related insomnia. Sleep EEG studies on hypnotic benzodiazepines show that tolerance tends to occur completely after one to four weeks with sleep EEG returning to pretreatment levels. The paper concluded that due to concerns about long term use both toxicity and tolerance and dependence as well as controversy over long term efficacy that wise prescribers should restrict benzodiazepines to a few weeks and avoid continuing prescriptions for months or years.A review of the literature found that non-pharmacological treatment options were a more effective treatment option for insomnia due to their sustained improvements in sleep quality.
Physical dependence
Temazepam like other benzodiazepine drugs can cause physical dependence and addiction. Withdrawal from temazepam or other benzodiazepines after regular use often leads to a benzodiazepine withdrawal syndrome, which resembles symptoms during alcohol and barbiturate withdrawal. The higher the dose and the longer the drug is taken for, the greater the risk of experiencing unpleasant withdrawal symptoms. Withdrawal symptoms can also occur from standard dosages and after short term use. Abrupt withdrawal from therapeutic doses of temazepam after long term use may result in a severe benzodiazepine withdrawal syndrome. Gradual and careful reduction of the dosage, preferably with a long-acting benzodiazepine with long half-life active metabolites such as chlordiazepoxide or diazepam is recommended, to prevent severe withdrawal syndromes from developing. Other hypnotic benzodiazepines are not recommended.A study in rats found that temazepam is cross tolerant with barbiturates and is able to effectively substitute for barbiturates and suppress barbiturate withdrawal signs.There are rare reports in the medical literature of psychotic states developing after abrupt withdrawal from benzodiazepines, even from therapeutic doses.Antipsychotics increase the severity of benzodiazepine withdrawal effects with an increase in the intensity and severity of convulsions.Patients who were treated in the hospital with temazepam or nitrazepam have continued taking these after leaving the hospital. It was recommended that hypnotics in the hospital be limited to 5 nights use only, to avoid the development of withdrawal symptoms like insomnia.
Medical research issues
The Journal of Clinical Sleep Medicine published a paper expressing concerns about benzodiazepine receptor agonist drugs, the benzodiazepines and the Z-drugs that are used as hypnotics in humans. The paper cites a systematic review of the medical literature concerning insomnia medications and states that almost all trials of sleep disorders and drugs are sponsored by the pharmaceutical industry while this is not the case in general medicine or psychiatry. It cites another study that "found that the odds ratio for finding results favorable to industry in industry-sponsored trials was 3.6 times as high as in non–industry-sponsored studies". Issues discussed regarding industry-sponsored studies include: comparison of a drug to a placebo, but not to an alternative treatment; unpublished studies with unfavorable outcomes; and trials organized around a placebo baseline followed by drug treatment, but not counterbalanced with parallel-placebo-controlled studies. Quoting a 1979 report that there was then, too, little research into hypnotics that was independent of the drug manufacturers, the authors conclude that "the public desperately needs an equipoised assessment of hypnotic benefits and risks" and that the NIH and VA should provide leadership to that end.
Pharmacology
It is a white, crystalline substance, is very slightly soluble in water and sparingly soluble in alcohol. The main pharmacological action of temazepam is to increase the effect of the neurotransmitter GABA (gamma-aminobutyric acid) at the GABAA receptor. This causes sedation, motor-impairment, ataxia, anxiolysis, anticonvulsant effect, muscle relaxation and reinforcing effect.As a premedication before surgery, temazepam decreased cortisol in elderly patients.In rats, temazepam triggered the release of vasopressin into paraventricular nucleus of the hypothalamus and decreased the release of ACTH under stress.
Pharmacokinetics
Oral administration of 15 to 45 mg temazepam in man resulted in rapid absorption with significant blood levels achieved in less than 30 minutes and peak levels at 2 to 3 hours.In a single and multiple dose absorption, distribution, metabolism, and excretion (ADME) study, using tritium (3H) labelled drug, temazepam was well absorbed and found to have minimal (8%) first pass drug metabolism. There were no active metabolites formed and the only significant metabolite present in blood was the O-conjugate. The unchanged drug was 96% bound to plasma proteins. The blood level decline of the parent drug was biphasic with the short half-life ranging from 0.4-0.6 hours and the terminal half-life from 3.5–18.4 hours (mean 8.8 hours), depending on the study population and method of determination.
Temazepam has very good bioavailability with almost 100% being absorbed from the gut. The drug is metabolized through conjugation and demethylation prior to excretion. Most of the drug is excreted in the urine, with about 20% appearing in the feces. The major metabolite was the O-conjugate of temazepam (90%); the O-conjugate of N-desmethyl temazepam was a minor metabolite (7%).
Interactions
As other benzodiazepines, temazepam produces additive CNS depressant effects when co-administered with other medications which themselves produce CNS depression, such as barbiturates, alcohol,opiates, tricyclic antidepressants, non-selective MAO inhibitors, phenothiazines and other antipsychotics, skeletal muscle relaxants, antihistamines and anaesthetics. Administration of theophylline or aminophylline has been shown to reduce the sedative effects of temazepam and other benzodiazepines.
Unlike many benzodiazepines, pharmacokinetic interactions involving the P450 system have not been observed with temazepam. Temazepam shows no significant interaction with CYP3A4 inhibitors (e.g. itraconazole, erythromycin).Oral contraceptives may decrease the effectiveness of temazepam and speed up its elimination half-life.
Overdose
Main article: Benzodiazepine overdose
Overdosage of temazepam results in increasing CNS effects, including:
Somnolence (difficulty staying awake)
Mental confusion
Respiratory depression
Hypotension
Impaired motor functions
Impaired or absent reflexes
Impaired coordination
Impaired balance
Dizziness
Coma
Death
Temazepam had the highest rate of drug intoxication, including overdose, among the common benzodiazepines in cases with and without combination with alcohol in a 1985 study.Temazepam and nitrazepam were the two benzodiazepines most commonly detected in overdose-related deaths in an Australian study of drug deaths.A 1993 British study found temazepam to have the highest number of deaths per million prescriptions among medications commonly prescribed in the 1980s (11.9, versus 5.9 for benzodiazepines overall, taken with or without alcohol).
A 1995 Australian study of patients admitted to hospital after benzodiazepine overdose corroborated these results, and found temazepam overdose much more likely to lead to coma in comparison to other benzodiazepines (odds ratio 1.86). The authors note that several factors, such as differences in potency, receptor affinity, and rate of absorption between benzodiazepines could explain this higher toxicity.
Although benzodiazepines have a high therapeutic index, temazepam is one of the more dangerous of this class of drugs.
The combination of alcohol and temazepam makes death by alcohol poisoning more likely.
