SLEEPING PILLS: BENZODIAZEPINE. REBOUND INSOMNIA.
It is now believed that benzodiazepine exerts an inhibitory effect on the transmission of signals between nerves, so that there is a slowing down in the relay of signals between nerve cells and hence the person becomes less excitable and more relaxed.
Benzodiazepine competes with a naturally occurring chemical in the nerve endings known as GABA (gamma amino butyric acid). It appears to displace GABA off these nerve endings, which increases the amount of freely available GABA. GABA is known to inhibit transmission of impulses between nerve cells.
There are two main kinds of benzodiazepine, the long acting and the short acting. By long action, we mean that once the drug is absorbed into the body it stays active for a long time and can be detected in the body after many days. The drug is eliminated from the body by two mechanisms, either destroyed by metabolism in the liver or excreted by the kidneys in the urine. The faster the metabolism, the shorter the half-life of the drug, which is the time taken for half of the drug in the body to be eliminated. This elimination phase can be much longer in older people than in younger people because their kidneys are not normally so efficient. The long acting hypnotic drugs have a long half-life and can sustain sleep longer, but they may give a hangover feeling the next morning; people who take these drugs often complain that they feel like a zombie the following morning. If this drug is taken nightly and regularly, it tends to accumulate in the body. One of the longer acting drugs is Flurazepam, commonly known as Dalmane, and its half-life is nearly 80 hours. This is rarely prescribed in Australia now.
The short acting benzodiazepine has a short half-life and is eliminated from the body much more quickly, usually within a few hours. It can initiate sleep more easily, but may not be as effective in sustaining sleep. There is very little hangover feeling in the morning and accumulation of the drug in the body is less likely even if taken regularly. A common short acting drug is Temazepam, which is marketed in Australia as Euhypnos or Normison; its half-life is 5.8 hours.
Health authorities all over the world have now recognized the abuse of benzodiazepines. They have found that they are addictive. As the number of deaths from barbiturates fell, it became apparent that quite a large number of people suffer from the distressing effects of dependence on benzodiazepines. In Australia alone there are about 6.5 million prescriptions for benzodiazepines written each year, and there are only 15 million people here.
Addiction means an increased tolerance of the body to the drug; hence a higher and higher dose is required to achieve the same drug effect. The body also becomes physically dependent on the drug to function effectively. If the drag is withdrawn suddenly, the body craves it, and the person experiences a whole range of psychological and physical symptoms. With benzodiazepine about 20 withdrawal symptoms have been described. These include tension, sweating, agitation, muscle ache, and irritability, but the most important is ‘rebound insomnia’.
In the sleep laboratory it is shown that REM sleep occupies about 25 per cent of the time spent in sleep. When a person takes sleeping pills, REM sleep is reduced to 5 or 10 per cent of sleep time, but if the pills are continued for many days the REM component gradually returns to 25 per cent. However, it has been shown that if sleeping pills are suddenly stopped there is an increase in REM sleep to about 40 per cent of sleep time, and, in the following nights, more dreams and nightmares are experienced. This is because the sleep induced by drugs is not a natural sleep—it has less of a REM component. When the drugs are stopped, there is a catch up in REM sleep, and this is called ‘rebound of REM sleep’ or ‘rebound insomnia’.
Initially benzodiazepine is prescribed for the treatment of insomnia arising from stress or some other reason. When the original stress is over, and the reason for taking these pills is gone, the drugs are stopped abruptly. This is when rebound insomnia sets in. People who suffer from rebound insomnia believe that they have lost the innate ability to sleep. This rebound insomnia is only transient and lasts just a few days. If these people persevere, the rebound insomnia passes and their sleep becomes normal again. However, there may be some who become psychologically dependent on these pills, meaning their confidence to sleep has disappeared..
It has also been shown that sleeping pills stop working after two weeks. The reason is that the body develops an increasing tolerance to the pills. The same dose of sleeping pill is no longer resulting in sleep as it used to. But then why do people persist in taking them? The answer is to prevent the withdrawal symptom—rebound insomnia.
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