What should I do if I have a reaction to my medication?

What to Do If You Have a Medication Reaction

Stop the medication immediately and seek medical attention—the severity of your symptoms determines whether you need emergency care (call 911 for breathing difficulty, severe hypotension, or generalized hives) or can contact your prescribing physician for milder symptoms like flushing or rash. 1

Immediate Actions Based on Symptom Severity

For Mild Reactions (flushing, rash, itching, pruritus)

• Stop taking the medication 1
• Contact your prescribing physician or healthcare provider promptly 1
• Document your symptoms with timing and description 1
• Do not restart the medication without medical evaluation 1

For Severe Reactions (shortness of breath, blood pressure changes, widespread hives, nausea/vomiting, chest tightness)

• Stop the medication immediately 1
• Call 911 or go to the emergency department 1
• If you have an epinephrine auto-injector and symptoms suggest anaphylaxis, use it immediately in the lateral thigh muscle 1
• Maintain consciousness of your airway, breathing, and circulation 1

For Life-Threatening Reactions (anaphylaxis with respiratory compromise, severe hypotension, generalized hives with breathing difficulty)

• Administer intramuscular epinephrine immediately (0.01 mg/kg, maximum 0.5 mL) into the lateral thigh 1, 2
• Call 911 immediately 1
• Lie flat with legs elevated if hypotensive, or sit upright if having breathing difficulty 1
• Repeat epinephrine every 5-15 minutes if symptoms persist 1

Critical Timing Considerations

Drug reactions can occur during medication administration, immediately after, or even days later, so remain vigilant for symptoms even after you've finished taking a dose 1. Reactions to certain chemotherapy drugs (platinum agents like carboplatin) typically occur after multiple exposures, while reactions to taxanes (paclitaxel, docetaxel) more commonly occur during the first few cycles 1.

What Medical Providers Will Do

Emergency Treatment

Medical staff will provide:

• Oxygen and airway support 1
• Intravenous fluids (1-2 liters normal saline rapidly if hypotensive) 1
• Antihistamines: Combined H1 blockers (diphenhydramine 25-50 mg) and H2 blockers (ranitidine 50 mg) work better than either alone 1
• Corticosteroids (methylprednisolone, hydrocortisone, or dexamethasone) to prevent biphasic reactions 1
• Additional epinephrine if initial dose ineffective 1
• Close monitoring for 24 hours after severe reactions 1

Diagnostic Evaluation

Your allergist or physician may:

• Obtain detailed history of the reaction timing, symptoms, and medication involved 1
• Measure tryptase levels (blood drawn 15 minutes to 3 hours after reaction onset) to confirm mast cell activation, though normal levels don't rule out drug allergy 1
• Perform skin testing for certain medications (particularly beta-lactam antibiotics and platinum chemotherapy agents) 1
• Consider drug provocation testing under controlled hospital conditions if diagnosis remains uncertain 3, 4

Future Medication Use

If You Had a Mild Reaction

• Do not take the medication again without allergist evaluation 1
• For mild infusion reactions to taxanes, rechallenge at a slower infusion rate may be possible under strict medical supervision with emergency equipment available 1
• Consultation with an allergist is strongly recommended before any rechallenge, especially for platinum drug reactions 1

If You Had a Severe or Life-Threatening Reaction

• Never take the implicated drug again 1
• Referral to an allergist or academic center with desensitization expertise is essential if the drug is still considered first-line therapy with no acceptable alternatives 1
• Desensitization protocols may be considered under specialist guidance, which involves administering gradually increasing doses over hours to induce temporary tolerance 1, 3
• Desensitization must be repeated with each treatment cycle and only maintains tolerance during continuous administration 3

Alternative Medications

• Your physician should prescribe alternative medications with unrelated chemical structures to avoid cross-reactivity 2
• Document your drug allergy clearly in your medical records and inform all healthcare providers 1, 2
• Consider wearing a medical alert bracelet for severe drug allergies 2

Important Caveats

Rechallenge after grade 3 or 4 reactions (severe or life-threatening) should not be attempted unless performed as formal desensitization by specialists in controlled settings 1. Even mild reactions to platinum chemotherapy agents can progress to severe reactions on subsequent exposures, making allergist consultation critical before any rechallenge 1. Patients taking beta-blockers may require glucagon (1-5 mg IV) rather than standard epinephrine dosing for refractory cardiovascular symptoms 1.