Immediately Discontinue Valproate and Initiate Ammonia-Lowering Therapy
This is valproate-induced hyperammonemic encephalopathy (VHE) causing delirium, and the valproate must be stopped immediately regardless of therapeutic levels. 1
Immediate Management Steps
1. Stop Valproate Now
- Discontinue sodium valproate completely - do not taper, as this is a medical emergency 1
- VHE can occur at therapeutic valproate levels and with normal liver function tests 2, 3
- The delirium will typically resolve within 24-72 hours after stopping valproate 4, 5, 2
2. Measure Ammonia Level Urgently
- Draw venous or arterial blood into lithium heparin or EDTA tube
- Transport on ice and process within 15 minutes 6
- A normal ammonia level would argue against VHE and require alternative diagnosis workup 7, 8
3. Initiate L-Carnitine Supplementation
- Give IV levocarnitine 50 mg/kg loading dose over 90 minutes, then 100-300 mg/kg/day 6
- This is critical as valproate depletes carnitine, which is the mechanism of hyperammonemia 9, 4
- Dramatic improvement typically occurs within 12-24 hours of carnitine initiation 4
4. Supportive Delirium Management
- Ensure adequate hydration with IV dextrose-containing fluids 6, 10
- Address hypoxia and optimize oxygen saturation 10
- Provide reorientation: visible clock/calendar, familiar caregivers, appropriate lighting 10
- Avoid benzodiazepines - contraindicated in decompensated states 8
- Check for and treat infection, dehydration, constipation, electrolyte abnormalities (especially hyponatremia) 10, 8
Bipolar Disorder Management Going Forward
Switch Mood Stabilizer
- Transition to lithium or carbamazepine for maintenance treatment 11
- Lithium requires close monitoring (renal function, thyroid, levels) but is first-line for bipolar maintenance 11
- Continue maintenance treatment for at least 2 years after last episode 11
Bridge with Antipsychotic if Needed
- If acute mood stabilization needed during transition, use haloperidol or second-generation antipsychotic 11
- Continue for at least 12 months after remission 11
Critical Pitfalls to Avoid
Do not restart valproate - this patient has demonstrated VHE and is at high risk for recurrence 3. At 75 years old, he is particularly vulnerable to this complication 12.
Do not wait for liver function tests - VHE occurs with normal LFTs in most cases 2, 3. The diagnosis is clinical plus elevated ammonia.
Do not assume therapeutic valproate levels are safe - VHE commonly occurs at therapeutic concentrations 5, 2, 3.
Monitor for rebound hyperammonemia - ammonia can transiently increase again after initial improvement, though this is less common with carnitine therapy 4.
Why This Happened
Valproate causes carnitine depletion, which impairs mitochondrial fatty acid oxidation and ammonia clearance 9, 4. This is an idiosyncratic reaction more common in elderly patients, those on long-term therapy, and those on high doses (this patient is on 2.5g/day total) 3, 12. The hypoactive delirium presentation (lethargy, confusion) is typical of VHE 5, 3.