Central nervous system medications are used to treat the effects of a wide variety of medical conditions, including Alzheimer's disease, depression, and Parkinson's disease. This category of medication also includes analgesics (pain medications), sedatives, and anticonvulsants.

Alzheimer's Disease Drugs

Several medications are available to help slow the decline in mental abilities in people who suffer from Alzheimer's disease, an incurable disease that causes gradual deterioration in brain function. These medications work by increasing the amount of a substance called acetylcholine in the brain. Commonly used medicines are donepezil, rivastigmine, and galantamine.

Amphetamines

Amphetamines, or adrenergic drugs, are sometimes prescribed as anorectics (drugs that are used to reduce the appetite). These drugs temporarily quiet the part of the brain that causes hunger, but they also keep a person awake, speed up the heart, and raise blood pressure. After two to three weeks, these medications begin to lose their effectiveness as appetite suppressants.

Amphetamines stimulate most people, but they have the opposite effect on children who have attention deficit hyperactivity disorder (ADHD), which is marked by inattention, impulsiveness, and an abnormal degree of overactivity. ADHD is difficult to diagnose properly and requires a specialist to treat. But when children with ADHD take an amphetamine such as methylphenidate, their level of activity diminishes. Most likely, amphetamines quiet these youngsters by selectively stimulating parts of the brain that ordinarily control activity.

Analgesics

Pain is not a disease but a symptom of some other problem. Drugs used to relieve pain are called analgesics, which form a rather diverse group. We do not fully understand how most analgesics work. Analgesics fall into two categories: They may be either narcotic or nonnarcotic.

Narcotics are derived from the opium poppy. They act on the brain to relieve pain, often bringing on drowsiness and a feeling of well-being. Some narcotics relieve coughing spasms and are used in prescription cough syrups. Unfortunately, narcotics can be addictive. To date, attempts by manufacturers to produce nonaddictive synthetic narcotic derivatives have not succeeded.

Nonnarcotic pain relievers are also used. Aspirin and related medications, called nonsteroidal anti-inflammatory drugs (NSAIDs), are the most frequently used pain relievers in the United States today. Aspirin does not require a prescription, but doctors often write prescriptions for it to treat diseases such as arthritis.

Acetaminophen, which is not an NSAID, may be used in place of aspirin to relieve pain, but it does not reduce inflammation.

A number of analgesic medications contain codeine or other narcotics in combination with nonnarcotic analgesics (such as aspirin, ibuprofen, or acetaminophen). These combination analgesics are not as potent as pure narcotics but are frequently as effective. Because these medications contain narcotics, however, they have the potential for abuse and must be used with caution.

Antianxiety/Sedative Drugs

Medications used in the treatment of anxiety, panic disorder, and insomnia selectively reduce the activity of certain chemicals in the brain. Drugs formulated to relieve anxiety include benzodiazepines (such as lorazepam, alprazolam, clorazepate, and diazepam) and buspirone. These medications are not offered to relieve the stresses of everyday life; they are used only when indicated by your doctor. Drugs used to induce sleep in insomniacs may include benzodiazepines, antihistamines (such as diphenhydramine), and zaleplon.

Anticonvulsants

Drugs such as carbamazepine, phenytoin, and gabapentin are used to control seizures and other symptoms of epilepsy. They selectively reduce excessive stimulation in the brain. In addition, these medications may be used to prevent and treat certain types of pain. The manner in which they work is not clearly understood.

Antidepressants

Tricyclic antidepressants (such as amitriptyline), selective serotonin reuptake inhibitors (such as fluoxetine, paroxetine, and sertraline), tetracyclic antidepressants (such as maprotiline), and monoamine oxidase (MAO) inhibitors (such as phenelzine) are types of medication used to treat depression. Antidepressant medications are also used for panic attacks and obsessive-compulsive disorder (OCD) and in the prevention of migraine headaches and other types of pain, although the manner in which they help to provide relief is not clearly understood.

Antidepressants may produce serious side effects, and they can interact with other drugs. MAO inhibitors can also mix with certain foods, resulting in dangerous increases in blood pressure. Therefore, they should be used very carefully.

Anti-inflammatory Drugs

Inflammation is the body's natural response to injury. An inflammatory response is generally marked by swelling, pain, fever, redness, and itching. Aspirin is one of the most effective anti-inflammatory drugs. Other drugs, called nonsteroidal anti-inflammatory drugs (NSAIDs) -- for example, fenoprofen, ibuprofen, indomethacin, naproxen, and tolmetin -- relieve inflammation and may be more effective than aspirin in certain individuals. Steroids are also used to treat inflammatory diseases.

When sore muscles tense up or tighten, they can cause pain, inflammation, and spasm. Skeletal muscle relaxants (such as orphenadrine and meprobamate) may help to relieve these symptoms. Skeletal muscle relaxants are often given in combination with an anti-inflammatory pain-relieving medication such as aspirin or ibuprofen. Some doctors, however, believe that aspirin or another NSAID and rest are better than skeletal muscle relaxants for alleviating the symptoms of muscle strain.

Antipsychotics

Major tranquilizers or antipsychotic medications are usually prescribed for patients who are suffering from psychoses (certain types of mental disorders). These medications calm certain areas of the brain but permit the rest of the brain to function normally. They act as a screen that allows the transmission of some nerve impulses but restricts the passage of others.

The drugs most frequently used include haloperidol, lithium, chlorpromazine, and thioridazine. Other newer agents that may be used include clozapine, olanzapine, and quetiapine.

Parkinson's Disease Drugs

Parkinson's disease is a progressive neurological disorder caused by a chemical imbalance in the brain. People who have Parkinson's disease experience uncontrollable tremors, develop a characteristic stoop, and eventually become unable to walk.

Medications such as benztropine, bromocriptine, levodopa, selegiline, and trihexyphenidyl are used to correct the chemical imbalance in the brain, thus helping to relieve the symptoms of the disease (although these medications can have unwanted side effects of their own). Benztropine and trihexyphenidyl are used to relieve tremors that are caused by other medications as well.