a. The Xanthine Derivatives. The xanthine derivatives have several pharmacological effects. One, they directly relax the smooth muscle of the bronchi and pulmonary blood vessels. By such dilation of the bronchi, more oxygen can be drawn into the lungs. Two, they stimulate the central nervous system and produce diuresis (they increase the production of urine) by direct action on the kidney. There are several examples of xanthine derivatives:
(1) Caffeine. Caffeine is found in coffee, tea, and in kola nuts (used to make some soft drinks). Caffeine is a stimulant that has been long used as a morning "picker-upper" for workers and students. Caffeine is found in some headache remedies products promoted to prevent drowsiness, and in some products designed to suppress appetite (in these preparations caffeine acts to stimulate the person). Although caffeine does have some desirable qualities (that is, small doses of the drug can promote better performance on tasks like typing and thinking), it is possible for a person to develop a psychological dependence on the drug. Withdrawal of the drug results in some persons' having mild withdrawal symptoms (for example, headaches).
(2) Aminophylline (Theophylline ethylenediamine). This drug is used in the treatment of bronchial asthma. It is given intravenously to provide rapid relief of pulmonary edema and dyspnea seen in the acute congestive heart failure patient because it increases cardiac output, slightly increases venous pressure, and relaxes the bronchial muscle. Side effects associated with the oral administration of this agent include nausea, vomiting, and nervousness. The patient should be informed to take this medication with food. The medication is supplied in 100 and 200-milligram tablets, 250
and 500-milligram suppositories, and in injectable form (25 milligrams per milliliter in a 10-milliliter ampule).
(3) Theophylline (Theo-dur®, Elixophyllin®). This xanthine derivative is used for the symptomatic relief of asthma because of its bronchial dilation effect. Theolair is but only one of many anhydrous theophylline products in use today. The side effects usually associated with the use of the drug are nausea, vomiting, and nervousness. The patient should be told to take theophylline with food. The drug is usually administered in a dosage of 3 to 5 milligrams per kilogram of body weight. It is supplied in various dosage forms (elixir, tablets, capsules, and sprinkles).
b. The Amphetamines. Many health care professionals are concerned about the abuse/misuse of the amphetamines. These Schedule II medications certainly have been abused in the past. Today, physicians and pharmacists cooperate to ensure these drugs are wisely used for medically acceptable purposes. Amphetamines act pharmacologically to produce two primary effects. One, they increase an individual's state of alertness. Two, they elevate a person's mood. Now, several agents will be discussed. The particular use(s) for each agent will be presented.
(1) Methylphenidate (Ritalin®). Methylphenidate (Ritalin®) is used to treat attention deficit hyperactivity disorder (ADHD), formerly known as minimal brain dysfunction, and narcolepsy. Observed abnormalities in ADHD include impulsiveness, short attention span, purposeless hyperactivity, emotional overreactivity, coordination and learning deficits, distractibility, and deficits in the perception of space, form, movement, and time. Since the first clinical sign seen with ADHD is purposeless hyperactivity, the terms hyperkinetic and hyperkinesia are sometimes used in place of attention deficit hyperactivity disorder (ADHD). Narcolepsy can be defined as an inability to stay awake. The most common side effect associated with this agent is nervousness. Methylphenidate is a Schedule II drug (Note R). The usual dosage of methylphenidate is 20 to 30 milligrams daily in divided doses. It is supplied in the form of 5 milligram, 10 milligram, and 20-milligram tablets.
(2) Dextroamphetamine sulfate (Dexedrine®). Dextroamphetamine was once prescribed as an anoretic (an appetite depressant) for many years. Recently, it has been found that dextroamphetamine's inhibitory effect on the appetite lasts only for four or five weeks. This finding, coupled with its increased abuse, has drastically reduced the quantity of the prescriptions for this drug. This agent is not used in the military for the inhibition of appetite. It is used only for the treatment of attention deficity hyperactivity disorder (ADHD) and narcolepsy. Most military and civilian physicians believe that exercise and the restriction of food (caloric) intake is the method of choice for weight reduction. The most common side effects associated with dextroamphetamine are nervousness and headaches. This drug has a very high abuse potential. It is controlled as a Schedule II (Note R) item. Dextroamphetamine is supplied in 5-milligram tablets, 10- and 15-milligram capsules.
(3) Methamphetamine hydrochloride (Desoxyn®). This drug is similar to dextroamphetamine in terms of its ability to suppress the appetite. However, its abuse potential is such that it is rarely used any longer for this purpose.
c. Other Agents. Many other drugs produce pharmacological effects similar to those produced by the amphetamines. These are most often used for their ability to suppress the patient's appetite. Sometimes you will find these medications combined with other drugs (for example, a sedative or an antianxiety agent) in order to counteract the stimulation they produce.
(1) Pemoline (Cylert®). This drug is used in the treatment of ADHD. It is usually prescribed in a graduated dose - beginning with a 37.5-milligram daily dose. It is then gradually increased at 1-week intervals of 18.75 milligrams until a desired clinical response is observed. The most common side effect seen with this agent is insomnia. Pemoline appears to have a lower abuse potential than methylphenidate; pemoline is classified as a Note Q drug. The drug is supplied in the form of 18.75, 37.5, and 75 milligram tablets.
(2) Diethylpropion hydrochloride (Tenuate®). Diethylpropion hydrochloride is used as an appetite suppressant. It is less effective in this use than the amphetamines. It produces such side effects as dryness of the mouth, nausea, and headaches. It is available in both 25-milligram tablets and 75-milligram (timed-release) tablets. Diethylpropion is a Note Q drug.
(3) Phendimetrazine tartrate (Prelu-2®). This drug is used as an appetite suppressant. Long-term use of the drug, especially in large doses, may produce psychic dependence. It produces such side effects as nervousness, excitement, euphoria, and dryness of the mouth. It is supplied in 35-mIlligram tablets and capsules and 105-milligram (timed-release) capsules. Phendimetrazine is a Note Q drug.
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