Question: Our ED physician gave a theophylline prescription to a patient with asthma, but the next day, she came back to say that she had nausea, nervousness, an increased heart rate and a severe headache. The doctor examined her and determined that she was having side effects from the medication. Do we report the diagnosis code for the asthma, or for the side effects? Codify Subscriber Answer: You may need to code both, but first, check the doctor's notes to determine whether the patient took the medication properly, since poisoning would be coded differently than an adverse reaction. However, assuming that your patient simply suffered an adverse reaction, you'll first code the symptoms. For example, in the case of the patient suffering from nausea, nervousness, increased heart rate and severe headache, coding the symptoms would involve R11.0 (Nausea), R45.0 (Nervousness), R00.0 (Tachycardia; unspecified) and R51 (Headache). In addition, you'll report T48.6X5A (Adverse effect of antiasthmatics, initial encounter) to reflect that the patient had adverse effects from taking the anti-asthmatic medication.