T36.91XD

Poisoning by unspecified systemic anti-infective and anti-parasitic, accidental (unintentional), subsequent encounter

T36.91XD is a specific ICD-10-CM code utilized for encounters involving the subsequent care of a patient who has experienced an accidental poisoning (overdose) of an unspecified systemic anti-infective or anti-parasitic agent. This includes antibiotics, antivirals, antifungals, or drugs used to treat parasitic infections where the exact substance was not identified or documented. The 'subsequent encounter' designation (indicated by the 7th character 'D') is applied when the patient is in the recovery or maintenance phase of treatment after the acute toxic effects have been initially managed. This phase typically involves monitoring for late-appearing complications such as renal dysfunction, hepatic stress, or the resolution of drug-induced dermatological reactions or neurotoxicity.

Clinical Symptoms

  • Residual gastrointestinal upset or nausea
  • Evidence of resolving drug-induced nephrotoxicity (fluctuating creatinine)
  • Elevated liver enzymes (ALT/AST) during recovery
  • Post-acute hypersensitivity reactions (resolving rashes or pruritus)
  • Tinnitus or vestibular imbalance (residual ototoxicity)
  • Secondary fungal infections (e.g., oral or vaginal candidiasis)
  • Resolution of neurotoxic effects like confusion or tremors
  • Electrolyte imbalances following acute toxicity management

Common Causes

  • Unintentional ingestion of incorrect medication
  • Accidental overdose due to cognitive impairment or confusion
  • Pediatric accidental ingestion of household medications
  • Pharmacy or caregiver dosing error
  • Accidental administration of a systemic anti-infective meant for another person
  • Environmental exposure leading to toxic absorption

Documentation & Coding Tips

Distinguish between active treatment and subsequent care for poisoning.

Example: Patient seen for follow-up of acute accidental antibiotic poisoning. Gastric lavage and initial stabilization were completed in the emergency department four days ago. Currently, the patient is in the recovery phase with resolving transaminitis. Vital signs are stable. No active acute poisoning symptoms are present. Documentation supports a subsequent encounter for healing and monitoring of secondary organ effects.

Billing Focus: Identify the encounter as subsequent (7th character D) because the patient is receiving routine care during the healing or recovery phase, not active treatment for the acute poisoning.

Document specific organ manifestations persisting into the subsequent phase.

Example: Reviewing renal function today following an accidental ingestion of a family member's anti-parasitic medication. Creatinine has improved from 2.1 to 1.3 mg/dL since discharge. This subsequent encounter focus remains on the resolving acute kidney injury secondary to unintentional systemic poisoning. Plan includes repeat BMP in one week to ensure return to baseline.

Billing Focus: Link the poisoning code (T36.91XD) to the specific manifestation codes, such as Acute Kidney Injury (N17.9), to demonstrate medical necessity for lab monitoring.

Clearly state the accidental nature and the specific agent if it becomes known.

Example: Follow-up for unintentional ingestion of an unknown anti-infective found in a hotel bathroom. Subsequent visit focused on monitoring for potential delayed neurologic toxicity. Intent remains confirmed as accidental poisoning. History obtained from the previous encounter in the ICU where toxicological screen was non-specific but suggestive of anti-parasitic toxicity.

Billing Focus: Use T36.91XD only when the specific anti-infective cannot be identified after clinical investigation. If the drug is later identified, update the code to a more specific T36 series code.

Detail the medical decision-making related to medication reconciliation.

Example: Conducted a complete medication reconciliation for a 72-year-old patient following a dosing error with systemic anti-infectives. The subsequent encounter includes evaluating the patient's ability to safely manage medications and assessing for residual vestibular damage. Medication adherence counseling provided to prevent further accidental poisoning events.

Billing Focus: Document time spent on medication reconciliation and counseling to support higher-level E/M services if time-based coding is utilized.

Specify the clinical status of the poisoning recovery.

Example: The patient is seen for the second follow-up visit after accidental poisoning by an unspecified anti-infective. The initial toxic reaction has subsided. Today's physical exam shows normal bowel sounds and no rash. The patient is clearing the substance from their system effectively. This encounter serves to confirm the absence of late-term complications like bone marrow suppression.

Billing Focus: Clinical status notes must confirm that active, emergency treatment is no longer required, justifying the use of the subsequent encounter suffix.

Relevant CPT Codes

Related Diagnoses

Hierarchy