ICD-10 Coding for Patients on Memantine
The ICD-10 code for a patient taking memantine depends on the specific dementia diagnosis, but the most common codes are G30.9 (Alzheimer's disease, unspecified) for moderate to severe Alzheimer's disease, F01.50 (vascular dementia without behavioral disturbance) for vascular dementia, or G31.83 (dementia with Lewy bodies) for Lewy body dementia—memantine is FDA-approved and guideline-recommended specifically for these conditions. 1, 2
Primary Diagnostic Codes Based on Memantine Indication
Alzheimer's Disease (Most Common)
- G30.9 - Alzheimer's disease, unspecified (use when severity not specified) 1, 2
- G30.0 - Alzheimer's disease with early onset (onset before age 65) 1
- G30.1 - Alzheimer's disease with late onset (onset at or after age 65) 1
- G30.8 - Other Alzheimer's disease 1
The American College of Neurology and Canadian Consensus Conference specifically recommend memantine for moderate to severe Alzheimer's disease, where it demonstrates 2-3 point improvements on cognitive testing measures. 1, 3
Vascular Dementia
- F01.50 - Vascular dementia without behavioral disturbance 1
- F01.51 - Vascular dementia with behavioral disturbance (if agitation, psychosis, or aggression present) 1
The Canadian Consensus Conference endorses memantine for vascular dementia based on demonstrated improvements in cognitive function and behavioral symptoms. 1
Other Approved Dementia Types
- G31.83 - Dementia with Lewy bodies 3, 1
- G31.83 - Parkinson's disease dementia (alternative: G20 with F02.80) 3, 1
Important Coding Considerations
Severity Specification
When coding Alzheimer's disease, add a fifth character to specify severity if documented:
- .x0 - Without behavioral disturbance 1
- .x1 - With behavioral disturbance (agitation, combativeness, wandering) 1, 4
Contraindicated Uses Requiring Different Codes
Memantine should be discontinued for indications other than AD, Parkinson's disease dementia, dementia with Lewy bodies, or vascular dementia. 3, 2 If prescribed for the following conditions, consider alternative coding:
- G31.09 - Frontotemporal dementia (memantine not recommended) 3
- G31.84 - Mild cognitive impairment (memantine should be deprescribed) 3
Behavioral Complications Requiring Additional Codes
If the patient has neuropsychiatric symptoms that influenced memantine prescribing:
- F06.8 - Other specified mental disorders due to known physiological condition (for dementia-related psychosis) 4
- R45.1 - Restlessness and agitation 4
The American Psychiatric Association notes that cholinesterase inhibitors (not memantine alone) may help reduce neuropsychiatric symptoms in patients with AD, Lewy body dementia, or Parkinson's disease dementia. 4
Clinical Context for Accurate Coding
Verify Appropriate Indication
Before finalizing the ICD-10 code, confirm memantine is being used for an approved indication. The Canadian Consensus Conference states memantine should only be continued for AD, PDD, DLB, or VD. 3 If prescribed off-label, document the specific rationale and use the most accurate dementia subtype code available.
Document Disease Severity
Memantine demonstrates high-certainty evidence of benefit only in moderate-to-severe AD (MMSE typically <20), with probable lack of benefit in mild AD (MMSE 20-23). 5, 6 Accurate severity coding helps justify continued use and reimbursement.
Consider Combination Therapy
If the patient is taking memantine plus a cholinesterase inhibitor (donepezil, rivastigmine, galantamine), this supports the moderate-to-severe AD diagnosis, as combination therapy shows additional benefits compared to ChEI monotherapy. 2, 7