Drug Allergy
 

Drug Allergy

Last Updated: May 31, 2001

Drug allergies are uncommon and unwanted side effects of medications. It is important to recognize the signs and symptoms of a drug allergy because they can be life threatening, although a reaction this severe is rare. Several different types of allergic reactions can occur. Reactions can range from a rash to arthritis to kidney problems. The body’s response can affect many organ systems, but the skin is the most frequent system involved.

Many drug allergies do not happen the first time you take a medication. The next time you take that medication a reaction can occur. You may have previously been exposed to the medication without being aware of it.

CAUSES

The most common causes of drug allergies are these:

  • Painkillers (called analgesics) such as codeine, morphine, nonsteroidal anti-inflammatory drugs (NSAIDs, such as ibuprofen or indomethacin), and aspirin
  • Antibiotics such as penicillin, sulfa drugs, and tetracycline
  • Antiseizure medications such as phenytoin (Dilantin) or carbamazepine (Tegretol)

SIGNS AND SYMPTOMS

Many different signs and symptoms of drug allergies may be present depending on the drug taken and how often you have taken it. These are the most common reactions:

  • Skin
    • Hives - Slightly red and raised swellings on the skin, irregular in shape, itchy
    • Photoallergy - Sensitivity to sunlight, an itchy and scaly rash when you go out in the sun
    • Erythema multiforme - Red, raised and itchy, sometimes look like bull's-eye targets, sometimes with swelling of the face or tongue
  • Serum sickness - Generally occurs within 1-2 weeks after exposure to a medication
    • Hives
    • Fever
    • Muscle and joint aches

    • Lymph node swelling

    • Inflammation of the kidney
  • Anaphylaxis or anaphylactoid - This is a life-threatening condition and must be cared for in an Emergency Department.
    • Skin reaction

    • Difficulty breathing

    • Fainting

    • Changes in vital signs (such as a decrease in blood pressure)
  

HOME CARE

After getting advice from your doctor, some mild allergic reactions may be treated at home.

  • For hives or skin reactions
    • Take cool showers or apply cool compresses.
    • Wear light clothing that doesn’t irritate your skin.
    • Take it easy. Keep your activity level low.
    • Apply calamine lotion or take over-the-counter antihistamines, such as diphenhydramine (Benadryl) or chlorpheniramine maleate (Chlor-Trimeton). (These medications may help the itching.)

WHEN TO CALL THE DOCTOR

You should always contact your doctor, or the doctor who prescribed a medication, if you are having a drug reaction. If you are having mild symptoms including itching and localized hives, first call the doctor who prescribed the medication to get advice. Your doctor may switch you to a different type of medication, recommend that you stop the medication, or, if appropriate, prescribe antihistamines to relieve your symptoms. If you cannot reach your doctor for advice quickly, play it safe and go to a hospital’s Emergency Department.

WHEN TO GO TO THE HOSPITAL

If you are having any body-wide symptoms such as fever, vomiting, throat swelling, or difficulty breathing, you should stop taking the medication and be seen immediately by a doctor.

If you are having difficulty breathing, your throat is swelling, or you are feeling faint, call 911 emergency services and go to a hospital’s Emergency Department immediately.

PHYSICIAN DIAGNOSIS

The diagnosis of a drug allergy is generally made by history and physical examination. Hives are usually easy for a doctor to recognize as is the "target" rash of erythema multiforme.

If you are having an unusual reaction such as serum sickness or anaphylaxis, you may need emergency medications, blood testing, and hospital admission.

PHYSICIAN TREATMENT

Generally, treatment of a drug allergy falls into 3 categories:

  • Mild allergy (minimal hives and itching)
    • Treatment is aimed at caring for the symptoms and stopping the body reaction caused by the drug.
    • Medications prescribed may include antihistamines, such as diphenhydramine (Benadryl), and you may be asked to stop taking the medication that caused the allergy.
  • Moderate allergy (body-wide hives and itching)
    • Treatment is aimed at caring for the symptoms and stopping the reaction.
    • Medications prescribed may include antihistamines such as diphenhydramine (Benadryl)), oral steroids (prednisone), or histamine blockers such as cimetidine (Tagamet), famotidine (Pepcid), or ranitidine (Zantac).
  • Severe allergy (shortness of breath, throat tightness, low blood pressure, severe hives, involvement of many organ systems)
    • Treatment is with strong medications to quickly reverse the dangerous chain of events.
    • This care may include antihistamines such as diphenhydramine (Benadryl), oral or IV steroids such as prednisone or methylprednisolone (Solu-Medrol), or histamine blockers such as cimetidine (Tagamet), famotidine (Pepcid), or ranitidine (Zantac).
    • Depending on the severity of other symptoms, other medications may be used including epinephrine (also called adrenaline) that is inhaled or given by IV or injected under the skin.

    • If your reaction is severe, you may need to be admitted to the hospital for continued therapy and observation.

PROGNOSIS

The prognosis of mild to moderate drug allergy is very good. With treatment and removal of the drug, most people will be much better within 48-72 hours.

The prognosis for a severe drug allergy is also good if you are seen by a doctor promptly and treatment is started. Some reactions can be life threatening, including serum sickness and anaphylaxis. These reactions to a drug will generally need admission to the hospital.

PREVENTION

The best prevention of drug allergies is taking as few medications as possible. The more exposure your body has to medications, the greater the likelihood of a drug allergy.

  • Tell your doctor about any adverse reactions in the past and the medications they occurred with before he or she prescribes medications to you.
  • Tell your doctor about any medications, prescription or over-the-counter, that you are taking.

FOLLOW-UP

Follow up with your doctor after you have been diagnosed with a drug allergy. This follow-up appointment can be used to reevaluate the treatment for your reaction and adjust any medications as needed.

If you do not respond to the treatment prescribed for your drug allergy, it is important that you see a doctor for reevaluation.

BIBLIOGRAPHY

  • Diasio RB: Principles of drug therapy. In: Cecil RL, Goldman L. Cecil Textbook of Medicine. 21st ed. WB Saunders Co; 2000:101, 1464-1466.
  • Eberst ME: Blood transfusions and component therapy. In: Tintinalli JE, Krome RL, Ruiz E, eds. Emergency Medicine: A Comprehensive Study Guide. McGraw-Hill; 1999.
  • Olson KR: Emergency evaluation and treatment. In:Poisoning and Drug Overdose. 3rd ed. Appleton & Lange; 1999.
  • Salomone JA: Anaphylaxis and acute allergic reactions. In: Tintinalli JE, Krome RL, Ruiz E, eds. Emergency Medicine: A Comprehensive Study Guide. McGraw-Hill; 1999.
  • Valentine MD: Allergy and related conditions. In: Barker, Burton, Zieve PD. Principles of Ambulatory Medicine. 5th ed. Lippincott Williams & Wilkins; 1999.

Home page, Drug information's ,Regional anesthesia ,Index for  diseases ,Index for  diseases, Perioperative medicine, Search engine, Accreditation, Learn Arabic Warfare, Anesthesia LINKS, Orthopedic LINKS, Midline

Constructed by Dr N.A. Nematallah Consultant in perioperative medicine and intensive therapy, Al Razi Orthopedic Hospital , State of Kuwait, email : razianesth@freeservers.com