In simple words: This code indicates the patient is experiencing negative effects from a drug that disrupts their body’s automatic functions, such as heart rate and breathing, and that this is not the first time they've sought care for this issue.

Adverse effect of unspecified drugs primarily affecting the autonomic nervous system, subsequent encounter. This code is used for patients who have experienced a harmful reaction to a drug that primarily impacts their autonomic nervous system, which controls involuntary bodily functions like heart rate, digestion, and breathing. This is a subsequent encounter, indicating the patient has previously received care for this condition.

Example 1: A patient who was previously prescribed a medication for high blood pressure returns to the doctor complaining of dizziness and lightheadedness. The doctor determines these are side effects of the medication acting on the autonomic nervous system and codes the encounter as T44.905D., A patient with Parkinson's disease experiences urinary incontinence as a side effect of their medication. After an initial consultation for this issue, the patient returns for follow-up management of the side effects, which is coded as T44.905D., A patient who was started on a new antidepressant medication previously experienced blurred vision and dry mouth, which were attributed to the medication's effect on the autonomic nervous system. They return for a follow-up appointment to discuss ongoing management of the side effects and this is coded with T44.905D.

Documentation should clearly support the diagnosis of adverse drug effects affecting the autonomic nervous system. The specific drug causing the reaction, the nature of the adverse effects, and evidence that this is a subsequent encounter should be clearly documented in the medical record.