Primary Care Coding Alert

Question: A patient came in complaining of vomiting following chemotherapy. The chemotherapy agent was taken as prescribed by the patient’s oncologist. Do I code this as if the patient is experiencing poisoning, toxic effect, or just an adverse reaction?

New York Subscriber

Answer: To code this scenario correctly, start your search at the ICD-10-CM Table of Drugs and Chemicals. Find explanations of the different types of drug toxicity below:

• Adverse effect: Problem that arises after taking a drug that has been correctly prescribed and properly administered
• Poisoning: Reaction to the improper use of a medication
• Underdosing: Taking less of a medication than is prescribed
• Toxic effect: Ingestion or contact with a harmful substance

Based on these definitions and the fact that the patient was taking the medication as prescribed, we can deduce that the patient is experiencing an adverse effect of the chemotherapeutic agent.

From the table, you can search under the terms “cancer chemotherapy drug regimen” to find the correct set of codes. Then, then select the code listed under “adverse effect.” To verify the full code, refer to the Tabular List. This will confirm the use of T45.1X5A (Adverse effect of antineoplastic and immunosuppressive drugs, initial encounter).

You still need to account for the vomiting, however. At this point, it’s important to consider context. Nausea and vomiting are typical side effects for patients undergoing chemotherapy, which means you will take a different route of coding this situation than if the effects were unintended or unexpected.

Section I.C.19.e.5.a of the 2023 ICD-10-CM guidelines tells you “when coding an adverse effect of a drug that has been correctly prescribed and properly administered, assign the appropriate code for the nature of the adverse effect followed by the appropriate code for the adverse effect of the drug (T36-T50). The code for the drug should have a 5th or 6th character “5” (for example T36.0X5-) Examples of the nature of an adverse effect are tachycardia, delirium, gastrointestinal hemorrhaging, vomiting ...”

Based on this guideline, you should code the vomiting first, followed by the adverse effect of chemotherapy code. In this scenario, you will report code R11.10 (Vomiting, unspecified) and for the adverse effect of the chemotherapy, you will use code T45.1X5A.