Drug Allergies
I.
Alternative
names
A. Allergic reaction
to a drug (medication)
B.
Definition
- a group of symptoms caused by allergic reaction to a drug (medication).
II.
Causes,
incidence, and risk factors
A.
Drug allergies occur when there is an allergic reaction to a medication.
1.
This is caused by hypersensitivity of the immune system, leading to a
misdirected response against a substance that does not cause a response in most
people.
2.
The body becomes sensitized (the immune system is triggered) by the first
exposure to the medication.
3.
The second or subsequent exposure causes an immune response.
B.
Reactions to drugs are uncommon, but almost any drug can cause an adverse
reaction.
1.
Reactions range from irritating or mild side effects (such as nausea and
vomiting), to allergic response, including life-threatening anaphylaxis.
2.
Some drug reactions are idiosyncratic (unusual effects of the
medication). For example, aspirin can cause nonallergic hives (no antibodies
formed), or it may trigger asthma.
C.
"True" drug allergies involve the production of antibodies and
the release of histamine and other chemicals.
1.
Most drug allergies cause minor skin rashes and hives.
2.
However, other symptoms occasionally develop and life-threatening acute
allergic reactions involving the whole body (anaphylaxis) can occur.
3.
Serum sickness is a delayed type of drug allergy that occurs a week or
more after exposure to a medication or vaccine.
D.
Penicillin and related antibiotics are the most common cause of drug
allergies.
E.
Other common allergic reaction causing
drugs include sulfa drugs, barbiturates, anticonvulsants, insulin preparations
(particularly animal sources of insulin), local anesthetics such as Novocain,
and iodine (found in many X-ray
contrast dyes).
1.
In drug allergy, which does depend on previous exposure, the reaction may
be immediate, especially if the drug is taken intravenously, or the reaction may
take a week to develop.
2.
Common allergic reactions to drugs such as insulin, penicillin, and
barbiturates include low fever, itchy rashes, and hives. Treatment consists of
discontinuing the medication.
F.
Probably the most drastic drug reaction is anaphylaxis
1.
A violent form of drug allergy.
2.
The first symptoms are all-over itchiness, especially on the soles of the
feet and the palms.
3.
The skin of the face and ears may swell, mimicking a bad sunburn.
4.
The bronchial muscle (the muscle in the airway leading to the lungs)
constricts, and the patient struggles for breath.
5.
The blood vessels dilate, blood pressure drops, and the patient faints.
6.
Deprived of oxygen, the brain and nervous system cannot narrow the blood
vessels again, and the body cannot recover without immediate medical aid.
7.
Treatment consists of epinephrine, a drug that constricts blood vessels
and dilates the bronchioles to open the airway.
8.
Steroid drugs may be given for a few days to aid recovery.
III.
Other signals of allergy
or serious adverse reaction to drugs
A.
Include bleeding, wheezing, vomiting, impaired sight or hearing, and
muscle weakness. Hives (itchy red lumps on the skin), headache, rashes, nausea,
and drowsiness are less serious side effects.
B.
A physician should be consulted when side effects occur.
C.
Often another drug can be substituted; sometimes the patient must learn
to tolerate the unpleasantness.
D.
A person who has experienced an allergic reaction to a drug should carry
a wallet card or wear an ID necklace or bracelet with the information even if
the initial reaction was slight.
E.
Subsequent exposure to the drug may provoke more severe reaction.
IV.
Types of Allergic
Reactions
A.
Mild Allergy
1.
Itching
2.
Rash or hives
3.
Headache
4.
Nausea and other GI symptoms
5.
Antihistamines can be used to prevent certain allergic responses.
However, because of their slow onset, they are not very effective in treating
reactions already underway.
B.
Anaphylactic Shock
1.
This is a life-threatening allergic response that occurs within 1 hour
(usually within minutes) of taking a drug.
2.
Emergency treatment is necessary.
3.
Treatment consists of an injection of epinephrine (adrenaline), which
opens the blood vessels and airways, antihistamines, and sometimes steroids.
Drug Allergies.
http://www.adam.com/ency/article/000819.htm.
1999. Adam.com
General
Treatment of Allergy Symptoms. http://allergies.about.com/cs/drugallergies/.
2000. Columbia University College
of P & S Complete Home Medical Guide.
Side Effects
and Drug Allergies. http://cpmcnet.columbia.edu/texts/guide/hmg34_0004.html.
2000. Columbia University College
of P & S Complete Home Medical Guide.