Lithium TID Dosing Schedule
For adults with normal renal function taking lithium three times daily, administer 300 mg at approximately 8-hour intervals (e.g., 8 AM, 4 PM, and midnight), though modern evidence strongly supports transitioning to once-daily evening dosing instead of continuing TID administration. 1
Standard TID Timing
- Space doses approximately 8 hours apart to maintain relatively stable serum concentrations throughout the 24-hour period 1
- Common schedules include morning, afternoon, and bedtime administration (e.g., 8 AM, 4 PM, 12 AM or 7 AM, 3 PM, 11 PM) 1
- The FDA label specifies 600 mg three times daily for acute mania, which translates to regular 8-hour intervals 1
Critical Reconsideration of TID Dosing
However, you should strongly consider switching to once-daily dosing rather than maintaining a TID schedule, as this represents current best practice:
Evidence Against TID Dosing
- Once-daily dosing produces equivalent efficacy to multiple daily doses with no significant difference in antimanic response 2, 3
- TID dosing causes significantly higher urinary frequency compared to once-daily administration (statistically significant on Day 21, p=0.008, and Day 42, p=0.035) 2
- Patients on twice-daily schedules required significantly higher total daily doses (p=0.017) and paradoxically achieved lower serum lithium levels (p<0.001) 2
- Compliance with midday doses is questionable, making TID schedules impractical in real-world settings 4
Advantages of Once-Daily Evening Dosing
- Single evening dosing prevents or limits polyuria and subsequent thirst, a major tolerability issue 3
- Improved compliance due to simplified regimen 4, 3
- No evidence suggests any clinical benefit from multiple daily doses over single dosing 3
- Modern sustained-release preparations support once-daily administration 4
Monitoring Requirements Regardless of Schedule
- Draw serum lithium levels 12 hours post-dose for standard formulations (or 24 hours for once-daily dosing) to ensure accurate therapeutic monitoring 1, 4
- Target therapeutic range is 0.6-1.2 mEq/L for maintenance, with 1.0-1.5 mEq/L for acute mania 1
- Toxicity begins at 1.5 mEq/L with serious toxicity at >2.0 mEq/L 5, 6
- Monitor serum levels twice weekly during acute phase until stabilized 1
Common Pitfall
The major pitfall is continuing TID dosing out of habit when once-daily evening dosing offers superior tolerability, particularly regarding renal side effects, without sacrificing efficacy 2, 3. If TID dosing must be maintained for specific clinical reasons, ensure strict 8-hour intervals and monitor for increased urinary symptoms 2.