Amphetamines
Definition
Amphetamines are a group of drugs that stimulate the central nervous system. Some of the brand names of amphetamines sold in the United States are Dexedrine, Biphetamine, Das, Dexampex, Ferndex, Oxydess II, Spancap No 1, Desoxyn, and Methampex. Some generic names of amphetamines include amphetamine, dextroamphetamine, and methamphetamine.
Purpose
Amphetamines stimulate the nervous system and are used in the treatment of depression, attention-deficit disorder, obesity , and narcolepsy , a disorder that causes individuals to fall asleep at inappropriate times during the day. Amphetamines produce considerable side effects and are especially toxic in large quantities. Amphetamines are commonly abused recreational drugs and are highly addictive.
Description
Amphetamines are usually given orally and their effects can last for hours. Amphetamines produce their effects by altering chemicals that transmit nerve messages in the body.
Recommended dosage
The typical dose for amphetamines in the treatment of narcolepsy in adults ranges from 5 mg to 60 mg per day. These daily doses are usually divided into at least two small doses taken during the day. Doses usually start on the low end of the range and are increased until the desired effects occur. Children over the age of 12 years with narcolepsy receive 10 mg per day initially. Children between the ages of six and 12 years start with 5 mg per day. The typical dose for adults with obesity ranges from 5 mg to 30 mg per day given in divided doses. The medication is usually given about one-half hour to one hour before meals.
The typical starting dose of amphetamines given to children with attention-deficit disorder over the age of six years is 5 mg per day. This is increased by 5 mg per day over a period of time until the desired effect is achieved. Children under the age of six years with this condition are usually started at 2.5 mg per day.
Precautions
People who are taking amphetamines should not stop taking these drugs suddenly. The dose should be lowered gradually and then discontinued. Amphetamines should only be used while under the supervision of a physician. People should generally take the drug early in the day so that it does not interfere with sleep at night. Hazardous activities should be avoided until the person's condition has been stabilized with medication. The effects of amphetamine can last up to 20 hours after the medication has last been taken. Amphetamine therapy given to women for medical reasons does not present a significant risk to the developing fetus for congenital disorders. In such cases, there may be mild withdrawal in the newborn. However, illicit use of amphetamines for non-medical reasons presents a significant risk to the fetus and the newborn because of uncontrolled doses.
Amphetamines are highly addictive and should be used only if alternative approaches have failed. They should be used with great caution in children under three years of age, anyone with a history of slightly elevated blood pressure, people with neurological tics, and in individuals with Tourette's syndrome. Amphetamines should not be taken by individuals with a history of an overactive thyroid, those with moderate-to-severe high blood pressure, those with the eye disease called glaucoma, those who have severe arteriosclerosis (hardening of the arteries), or anyone with psychotic symptoms ( hallucinations and delusions ). Individuals with a history of drug abuse, psychological agitation, or cardiovascular system disease should also not receive amphetamine therapy. In addition, patients who have taken MAO inhibitors, a type of antidepressant, within the last 14 days should not receive amphetamines. MAO inhibitors include phenelzine (Nardil), and tranylcypromine (Parnate).
Side effects
The most common side effects that are associated with amphetamines include the development of an irregular heartbeat, increased heart rate, increased blood pressure, dizziness, insomnia , restlessness, headache, shakiness, dry mouth, metallic taste, diarrhea, constipation, and weight loss. Other side effects can include changes in sexual drive, nausea, vomiting, allergic reactions, chills, depression, irritability, and other problems involving the digestive system. High doses, whether for medical purposes or illicit ones, can cause addiction , dependence, increased aggression, and, in some cases, psychotic episodes.
Interactions
Patients taking amphetamines should always tell their physicians and dentists that they are using this medication. Patients should consult their physician before taking any over-the-counter medication while taking amphetamines. The interaction between over-the-counter cold medications with amphetamine, for instance, is particularly dangerous because this combination can significantly increase blood pressure. Such cold medications should be avoided when using amphetamine unless a physician has carefully analyzed the combination.
The combination of amphetamines and antacids slows down the ability of the body to eliminate the amphetamine. Furazolidone (Furoxone) combined with amphetamine can significantly increase blood pressure. Sodium bicarbonate can reduce the amount of amphetamine eliminated from the body and dangerously increase amphetamine levels in the body. Certain medications taken to control high blood pressure, including guanadrel (Hylorel) and guanethidine (Ismelin), MAO inhibitors, and selegiline (Eldepryl) should not be used in conjunction with amphetamines. In addition, tricyclic antidepressants [including desipramine (Norpramin) and imipramine (Tofranil)], antihistamines, and anticonvulsant drugs should not be combined with amphetamines.
Resources
BOOKS
Consumer Reports staff. Consumer Reports Complete Drug Reference. 2002 ed. Denver: Micromedex Thomson Healthcare, 2001.
Ellsworth, Allan J. and others. Mosby's Medical Drug Reference, 2001–2002. St. Louis: Mosby, 2001.
Hardman, Joel G. and Lee E. Limbird, eds. Goodman & Gilman's The Pharmacological Basis of Therapeutics. 10th ed. New York: McGraw-Hill, 2001.
Mosby's GenRx Staff. Mosby's GenRx. 9th ed. St. Louis: Mosby, 1999.
Venes, Donald and Clayton L. Thomas. Taber's Cyclopedic Medical Dictionary. 19th ed. Philadelphia: F. A. Davis, 2001.
Mark Mitchell, M.D.
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