Brain and Nervous System

Disorders of the brain and nervous system can manifest themselves as illnesses with predominant physical impairments (for example: epilepsy, strokes) or as illnesses with predominant mental and emotional impairments (for example: schizophrenia or depression).

These illnesses can result from different types of disorders of the brain and nervous system. Death of neurons resulting from poor circulation can be the cause of paralysis; electrical disturbances of certain brain neurons produce the seizures of epilepsy. Temporary changes to blood circulation within and around the brain are thought to be the principal cause of migraine headaches. The exact brain disorder causing mental and emotional impairments such as schizophrenia or depression is not known. Nevertheless, scientific evidence indicates that a malfunction of neurons and neurotransmitters might be implicated. For example, there might be too much or too little neurotransmitter in a brain region or the neurons might be underactive, overactive, or poorly coordinated.

Analgesics

Analgesics are medicaments that relieve pain. For many disorders, the relief of pain is one of the most important aspects of treatment. Since pain is not a disease but a symptom, long-term relief depends on treatment of the underlying cause. For example, the pain of toothache can be relieved by medicaments but can only be cured by appropriate dental treatment.

Damage to body tissue as a result of disease or injury is detected by nerve endings that transmit signals to the brain, where they are interpreted. The interpretation of these sensations can be affected by the psychological state of the individual, so that pain is worsened by anxiety and fear, for example. Often a reassuring explanation of the cause of discomfort can make pain easier to bear. Because of these psychological factors, sleeping medicaments, anti-anxiety medicaments, or antidepressants are sometimes prescribed in addition to, or instead of, analgesics, particularly in pain requiring many months of treatment.

Narcotics and non-narcotics are the two principal types of analgesics. Also, local anesthetics are commonly used to relieve pain. Narcotics such as morphine are the most powerful analgesics but cause drowsiness. Non-narcotic medicaments include ASA, acetaminophen, and non-steroidal anti-inflammatory medicaments (NSAIDs) and may provide adequate pain relief without drowsiness.

Narcotics act directly on the brain and spinal cord to alter the perception of pain. They thus act like the endorphins, hormones naturally produced in the brain that stop the cell-to-cell transmission of pain sensation. Non-narcotics prevent stimulation of the nerve endings at the site of the pain.

When pain is treated under medical supervision, it is common to start with a non-narcotic, and if this provides inadequate relief, to change to a combination medicament (a mixture of a mild narcotic and a non-narcotic). A strong narcotic may be used if the less powerful medicaments are ineffective. More severe (e.g., postoperative) or long-lasting continuous pain may be treated by injections of narcotics. When treating pain with an over-the-counter preparation, for example, taking ASA for a headache, you should seek medical advice if pain persists for longer than 48 hours, recurs, or is worse or different from previous pain.

Sleeping medicaments

Difficulty in getting to sleep or staying asleep (insomnia) has many causes. Most people suffer from sleepless nights from time to time, usually as a result of a temporary worry or discomfort from a minor illness. Persistent sleeplessness can be caused by psychological problems including anxiety or depression, or by pain and discomfort arising from a physical disorder.

Most sleeping medicaments promote sleep by depressing brain function. They interfere with chemical activity in the brain and nervous system by reducing communication between nerve cells. This leads to a reduction in brain activity, allowing you to fall asleep more easily.

A sleeping medicament rapidly produces drowsiness and slowed reactions. Some people find that the medicament makes them appear to be drunk and slurs their speech, especially if they delay going to bed after taking their dose. Most people find they usually fall asleep within one hour of taking the medicament.

Because the sleep induced by medicaments is not the same as normal sleep, many people find they do not feel as well rested by it as by a night of natural sleep. This is the result of suppressed brain activity. Sleeping medicaments also suppress the sleep during which dreams occur, and both dream sleep and non-dream sleep are essential components for a good night's sleep.

Some people experience a variety of "hangover" effects the following day. The benzodiazepines may produce minor side effects, such as daytime drowsiness, dizziness, and unsteadiness, that can impair the ability to drive or operate dangerous machinery. Elderly people are especially likely to become confused; for them, selection of an appropriate medicament is particularly important.

Most sleeping medicaments can produce psychological and physical dependence when taken regularly for more than a few weeks, especially if taken in larger-than-normal doses. If they are withdrawn abruptly, sleeplessness, anxiety, seizures, and hallucinations can arise. Nightmares and vivid dreams may occur because the amount of time spent in dream sleep increases. Anyone who has been using sleeping medicaments regularly for a long time and wishes to stop taking them should seek his or her physician's advice on how to reduce dosage gradually so as to avoid withdrawal symptoms.

One of the risks of taking sleeping medicaments for a prolonged period is that there may be a temptation to exceed the prescribed dose, especially if the person has been taking them for some weeks and their effect has diminished. While it is inadvisable to take more than the prescribed dose of any medicament, overdose can be a particular risk with the barbiturates.

Anti-anxiety medicaments

Anxiety can be a normal reaction to real dangers or to stressful periods of everyday life. It can be beneficial, providing a stimulus to cope with challenges. However, some individuals can chronically experience moderate to severe anxiety when there is no real danger or stressful situation. Their excessive anxiety is often accompanied by an overactivity of the sympathetic nervous system manifested by physical symptoms: shaking, palpitations, breathlessness, sweating, and digestive distress. Some individuals may also experience sudden attacks of anxiety, fear, or panic, accompanied by these physical symptoms. These attacks are called panic attacks.

It is thought that the benzodiazepines depress activity in the part of the brain that controls emotion, by promoting the action of a chemical called gammaaminobutyric acid (GABA). GABA attaches itself to brain cells, blocking transmission of electrical impulses. This reduces communication between brain cells. Benzodiazepines are thought to increase the inhibitory effect of GABA on brain cells, thus preventing excessive brain activity, which causes anxiety.

Benzodiazepines reduce feelings of agitation and restlessness, slow mental activity, and often produce drowsiness. They are said to reduce motivation and, if taken in large doses, may lead to apathy. They also have a relaxing effect on the muscles, and some benzodiazepines are used specifically for that purpose. Minor adverse effects of these medicaments include dizziness and forgetfulness. People who need to drive or operate dangerous machinery should be aware that their reactions may be slowed. Because the brain soon becomes tolerant to their effects, benzodiazepines may become less effective after a few weeks.

The benzodiazepines are considered safe for most people. The main risk is that people who take them regularly may become psychologically and physically dependent, particularly when large doses have been used. For this reason they are usually given for courses of two weeks or less. However, benzodiazepines are sometimes used on a long-term basis for cases of chronic, severe anxiety or panic attacks. The therapeutic benefit in such cases has to be weighed against a potential dependency. If a person has been taking them for a long period, they are normally withdrawn gradually under medical supervision. If they are stopped suddenly, withdrawal symptoms, including excessive anxiety, nightmares, and restlessness, may occur. Benzodiazepines have been abused for their sedative effect, and they are therefore prescribed with particular caution for people with a history of drug or alcohol abuse.

Antidepressant medicaments

Occasional moods of sadness or discouragement are normal and usually pass quickly. But more severe depression, accompanied by despair, lethargy, loss of sex drive, apathy, and poor appetite, may call for medical attention. Such depression can arise from the death of someone close, an illness, or sometimes from no apparent cause.

There are three main types of medicaments used to treat depression: tricyclics, monoamine oxidase inhibitors, and selective serotonin reuptake inhibitors. Other antidepressants, such as maprotiline, have actions similar to those of the tricyclics.

No one yet knows precisely how antidepressants produce their beneficial effect. However, research indicates that they can act on several types of neurons by either increasing or decreasing their electrical activity; these complex effects on neurons and their receptors seem to be related to their therapeutic effect.

The beneficial effect of antidepressants is usually noticeable after 10 to 14 days. But it may be six to eight weeks before you feel the full effect. However, within the first day of treatment some of the tricyclics can produce drowsiness and a variety of anticholinergic effects including dry mouth, blurred vision, and difficulty urinating.

Tricyclics and MAOls are dangerous in overdose: tricyclics can produce coma, cause seizures, and possibly fatal abnormal heart rhythms; MAOls can also cause seizures and even death. Both are prescribed with caution for those with heart problems or epilepsy.

Monoamine oxidase inhibitors have numerous side effects because they deactivate enzymes in the body that normally break down certain chemicals (particularly tyramine) found in some foods. MAOls taken with certain medicaments or foods rich in tyramine (for example, cheese, meat or yeast extracts, and red wine) can produce a dramatic rise in blood pressure even two weeks after stopping the medicament. A newer MAOI, moclobemide, is much less likely to lead to unwanted symptoms when taken with food, and restrictions in diet are not usually needed.

Antipsychotic medicaments

"Psychosis" is a term used to describe mental disorders that prevent the sufferer from thinking clearly, recognizing reality, and acting rationally. These disorders include schizophrenia, manic depression, and paranoia. The precise causes of these disorders are unknown, although a number of factors, including stress, heredity, and brain injury, may be involved. Temporary psychosis can also arise as a result of alcohol withdrawal or the abuse of mind-altering medicaments. A variety of medicaments are used to treat psychotic disorders, most of which have similar actions and effects. One exception is lithium, which is particularly useful for manic depression.

It is thought that some forms of mental illness are caused by an increase in communication between brain cells due to overactivity of a chemical called dopamine. This may disturb normal thought processes and produce abnormal behavior. Dopamine combines with receptors on the brain cells. Antipsychotics reduce the transmission of nerve signals by binding to these receptors, thus making the brain cells less sensitive to dopamine.

By modifying abnormal behavior, the antipsychotics enable the sufferer to live outside of a mental institution, where psychotic patients were usually confined up until the 1950s.

Because antipsychotics depress the action of dopamine, they can disturb its balance with another chemical in the brain, acetylcholine. If that occurs, signs like those of parkinsonism can appear -for example, the expressionless face and shaky hands. In those circumstances, a change in medication becomes necessary, or an additional medicament may be prescribed to counteract the adverse effects of the antipsychotic.

Antipsychotics may also block the action of another neurotransmitter, norepinephrine. This lowers the blood pressure, especially when you stand up, causing dizziness. It may also prevent ejaculation.

It is important to continue taking these medicaments even if all symptoms have gone, because symptoms are controlled only by taking the prescribed dose.

Because these medicaments can have permanent as well as temporary side effects, the minimum necessary dosage is used. This is found by starting with a low dose and increasing it until symptoms are controlled. The dose is reduced gradually when medicament treatment needs to be stopped.

The most serious long-term risk of antipsychotic treatment is a disorder known as tardive dyskinesia, which may develop after one to five years. This consists of repeated jerking movements of the mouth, tongue, and face, and sometimes the hands and feet. Some physicians have suggested that periodic withdrawal of the medicament for several months may reduce the severity of this condition, but the value of such "medicament holidays" has not been proved.

Anticonvulsant medicaments

Electrical signals from nerve cells in the brain are normally finely coordinated to produce smooth movements of arms and legs. But these signals can become paroxysmal and chaotic, and trigger the disorderly muscular activity and mental changes which are characteristic of a seizure (also called a fit or convulsion). The most common cause of seizures is the disorder known as epilepsy. However, seizures may also be brought on by outside stimuli -such as flashing lights - or caused by brain disease or injury, by the toxic effects of certain medicaments, or, in young children, by a high temperature. Anticonvulsant medicaments are used to reduce the risk of a seizure and to stop one that is in progress.

Brain cells bring about body movement by a form of electrical activity which passes through the nerves to the muscles. In a seizure, excessive electrical activity starts in one part of the brain and spreads to other parts, causing uncontrolled stimulation of brain cells.

Most anticonvulsant medicaments have an inhibitory effect on brain cells and damp down electrical activity, thus preventing the excessive buildup which causes a seizure.

Ideally, the only effect an anticonvulsant should have is to reduce or prevent seizures. Unfortunately, no medicament prevents seizures without potentially affecting normal brain function, leading to poor memory, inability to concentrate, lack of coordination, and lethargy. It is important, therefore, to find a dosage that is sufficient to prevent seizures without causing unacceptable side effects. The dose has to be carefully tailored to the individual there is no standard dose for anticonvulsants. It is usual to start with a low dose of a selected medicament and to increase it gradually until a balance is achieved between the effective control of seizures, and the occurrence of side effects, many of which wear off after the first few weeks of treatment. Blood tests to monitor levels of the medicament in the body are usually carried out periodically. Finding the correct dose may take several months. It may sometimes be necessary to use more than one medicament to adequately control seizures.

Each anticonvulsant medicament has its own specific adverse effects and risks. In addition, most of them affect the liver's ability to break down other medicaments and so may influence the action of other medicaments you are taking. Physicians try to use the minimum number of anticonvulsants in anyone person in order to reduce the risk of such interactions occurring.

People taking anticonvulsants need to be particularly careful to take their medication regularly as prescribed. If the levels of the anticonvulsant in the body are allowed to fall suddenly, seizures are very likely to occur. The reason for this is that without the inhibitory medicament, there is little to stop the buildup of electrical activity that brings on seizures. Accordingly, the dose should not be reduced or the treatment stopped except on the advice of a physician. If, for any reason, treatment with anticonvulsants is to be stopped, the dose should be reduced gradually, usually over a period of months. People on anticonvulsant therapy are advised to carry an identification tag that gives full details of their condition and treatment.

Antiparkinsonism medicaments

Antiparkinsonism medicaments are used in the treatment of parkinsonism. This is the general term used to describe shaking of the head and limbs, muscular stiffness, an expressionless face, and inability to control or initiate movement. It is caused by an imbalance between the chemicals dopamine and acetylcholine in the brain. These chemicals transmit nerve signals in the part of the brain that coordinates movement. They have opposing actions and are normally finely balanced. In parkinsonism there is a reduction in the action of dopamine, so that the effect of acetylcholine is increased.

Parkinsonism has a variety of causes, but the most common is degeneration of the dopamine-producing cells in the brain, known as Parkinson's disease. Other causes include the side effects of certain medicaments, notably antipsychotics, brain damage, and narrowing of the blood vessels to the brain.

Antiparkinsonism medicaments restore the balance between dopamine and acetyl- choline. They fall into two main groups: those medicaments that act by reducing the effect of acetylcholine (anticholinergic medicaments) and those that act by boosting the effect of dopamine.

Each type of medicament relieves some symptoms of parkinsonism better than others, although it is difficult to control symptoms in the more advanced stage of the disease. Anticholinergics improve stiffness more than shaking or the inability to initiate movement, and benefit is felt within a few days. They also reduce excessive salivation: dribbling is often a problem in Parkinson's disease.

Levodopa often produces a dramatic improvement in all symptoms. Side effects of levodopa include nausea, vomiting, and flushing. When given in excess it can also cause involuntary movements in the face and the body. Although these problems may be alleviated by reducing the dose, as the disease progresses it becomes increasingly difficult to give sufficient levodopa to improve symptoms without causing side effects. Also, in the later stage of the disease, the effect of each dose wears off before the next one is taken, and it may be necessary to take the medicament more frequently.

Amantadine relieves all symptoms of parkinsonism in people with mild to moderate cases. It has few side effects but the beneficial effect may wear off over a few months. The most common side effects of bromocriptine and selegiline are the same as those produced by levodopa.

Nervous system stimulants

A person's state of mental alertness varies throughout the day and is under the control of chemicals in the brain, some of which are depressant (causing drowsiness) and others that are stimulant (heightening awareness).

It is thought that an increase in the activity of the depressant chemicals may be responsible for a rare condition called narcolepsy, a tendency to fall asleep for no obvious reason. Nervous system stimulants are given to increase wakefulness. They include the amphetamines and related medicaments, notably methylphenidate. Respiratory stimulants, including caffeine (found in coffee, tea, and cola), are used to improve breathing.

The level of wakefulness is controlled by a part of the brain stem called the reticular activating system (RAS). Activity here depends on the balance between chemicals, some of which are excitatory (including norepinephrine) and some inhibitory (such as gamma-aminobutyric acid). Stimulants promote the release of norepinephrine, increasing activity in the RAS and other parts of the brain, so raising the level of alertness.

In adults, central nervous system stimulants taken in the prescribed dose for narcolepsy increase wakefulness allowing normal concentration and thought processes to occur. They may also reduce appetite and cause tremors. In hyperactive children they reduce the general level of activity to a more normal level and increase the attention span.

Some people, especially the elderly or those with previous psychiatric problems, are particularly sensitive to stimulants and may experience adverse effects, even when the medicaments are given in comparatively low doses. They are used with caution in children because they can retard growth if taken for prolonged periods. In a child, an excess of these medicaments depresses the nervous system, producing drowsiness or possibly loss of consciousness. Palpitations may occur.

These medicaments reduce the level of natural stimulants in the brain, so that after a few weeks' regular use a person may become physically dependent on them for normal function. If they are then abruptly withdrawn, the excess of natural inhibitory chemicals in the brain depresses activity in the central nervous system, producing withdrawal symptoms. These may include lethargy, depression, and increased appetite.

If used by adults in excess or inappropriately, stimulants can produce over-activity in the brain, resulting in extreme restlessness, sleeplessness, and feelings of nervousness or anxiety. They also stimulate the sympathetic branch of the autonomic nervous system, causing shaking, sweating, and palpitations. More serious risks of exceeding the prescribed dose are seizures and a disturbance in mental functioning that may result in delusions and hallucinations.

Migraine medicaments

Migraine is a term applied to recurrent severe headaches affecting only one side of the head and caused by changes in the blood vessels. Such headaches may be accompanied by nausea and vomiting and preceded by flashing lights or numbness and tingling in the arms. Occasionally, speech may be impaired, and the attack may be disabling. The exact cause of migraine is unknown, but an attack may be triggered by excitement, tension, shock, physical exertion, a blow to the head, some foods, and some medicaments. Victims often have a family history of migraine.

A migraine attack begins when blood vessels surrounding the brain constrict. This is thought to be caused by certain chemicals in food or produced in the body. Methysergide and propranolol block the effect of the chemicals on blood vessels and so prevent attacks.

The next stage occurs when blood vessels in the scalp and around the eyes dilate, releasing pain-producing chemicals called prostaglandins. ASA and acetaminophen relieve pain by blocking the production of prostaglandins, while codeine acts directly on the brain to alter the perception of pain. Ergotamine and sumatriptan relieve pain by narrowing the dilated blood vessels.

All these medicaments have their own side effects. Sumatriptan may cause chest tightness. Ergotamine may cause drowsiness, tingling sensations in the skin (paresthesia), cramps, weakness in the legs, and pain in the abdomen, arms, and legs.

Ergotamine should be used with caution if you have poor circulation because it can damage blood vessels through prolonged over constriction. Frequent use can lead to dependence and numerous adverse effects, including headache. You should not take more than your physician advises in any one week. Ergotamine should not be used if you have an infection because it can restrict blood flow to the site of infection and delay recovery. Sumatriptan should not be used if you are taking ergotamine or if you suffer from coronary heart disease, angina, or high blood pressure.

Methysergide can produce pain in the abdomen or lower back, and also shortness of breath due to an unusual type of damage to tissues.

Anti-emetic medicaments

Anti-emetic medicaments are used to suppress vomiting and nausea. Vomiting (emesis) is a reflex action that protects the body by expelling harmful substances. Common causes of vomiting and nausea are digestive tract infection, pregnancy, motion sickness, and vertigo. They can also occur as a side effect of a medication, or medicament or radiation therapy for cancer.

The main anti-emetic medicaments are metoclopramide, domperidone, ondansetron, the antihistamines, and phenothiazine medicaments, which are also used to treat mental illness. Nabilone, a marijuana derivative, may be used in cancer patients needing an anti-emetic.

Nausea and vomiting occur when a specialized part of the brain called the vomiting center is stimulated by signals which may arise from various points in the brain and body: from the digestive system, from the part of the brain that is responsible for consciousness, or from the inner ear. Signals may also arise from an area of the brain called the chemoreceptor trigger, which stimulates the vomiting (emetic) center if it detects any harmful substances present in the blood. Anti-emetic medicaments may act at one or more of these places in the body. In addition, these medicaments may also promote the normal emptying of the stomach contents into the intestine.

In addition to reducing or preventing vomiting and nausea, most anti-emetics may make you feel drowsy. Certain non-sedating antihistamines may therefore be preferred for the prevention of motion sickness.

Because the antihistamines block the parasympathetic system, they can produce many anticholinergic side effects, including dry mouth, blurred vision, and difficulty passing urine. Phenothiazine medicaments -which also may produce anticholinergic side effects -can produce dizziness.

Allergy
Eyes and Ears
Gastrointestinal Tract
Heart and Circulation
Hormones and Endocrine System
Infections and Infestations
Malignant and Immune Disease
Muscles, and Joints
Reproductive and Urinary Tracts
Respiratory System
Skin