Yes, lithium ER 1200 mg can be dosed once daily at bedtime
Once-daily bedtime dosing of lithium ER 1200 mg is appropriate and may offer advantages over divided dosing, including improved adherence and potentially reduced side effects, particularly tremor and polyuria. The extended-release formulation is specifically designed to allow for once-daily administration while maintaining therapeutic lithium levels.
Pharmacokinetic Rationale
Extended-release lithium formulations reach peak plasma concentrations at 4-5 hours (compared to 1-2 hours for immediate-release), with bioavailability of 80-100% and an elimination half-life of 18-36 hours 1. This pharmacokinetic profile supports once-daily dosing. The sustained-release preparation results in 30-50% reductions in peak plasma concentrations without major changes in overall drug exposure 1.
Clinical Evidence Supporting Once-Daily Dosing
Multiple studies demonstrate that single daily dosing is both feasible and potentially superior to divided dosing:
- Single evening dosing prevents or limits increases in urine output and subsequent thirst, addressing common tolerability issues 2
- Patients receiving once-daily dosing with sustained-release preparations maintaining 12-hour plasma levels around 0.6 mmol/L showed decreased affective morbidity and fewer side effects (including reduced tremor and lower TSH levels) compared to conventional divided dosing 3
- A recent randomized trial found that switching to prolonged-release lithium significantly improved tremor in 62.9% of patients versus 20.0% with immediate-release formulations, with benefits persisting at 12 weeks 4
- A 2-year comparative study showed prolonged-release lithium provided similar clinical efficacy to immediate-release but with fewer side effects (particularly tremor and gastrointestinal issues) and better adherence 5
Monitoring Considerations
Draw lithium levels 12 hours after the evening dose, not 24 hours. Despite once-daily dosing, the standard 12-hour blood draw remains appropriate because:
- By 12 hours post-dose with extended-release formulations, blood levels are essentially identical to immediate-release formulations 6
- This allows comparison with the extensive published literature based on standard 12-hour draws 6
- The 24-hour level would be a trough that doesn't correlate well with established therapeutic ranges
Target therapeutic range remains 0.6-0.8 mmol/L for most patients, though some sources suggest 0.8-1.0 mmol/L for sustained-release preparations 1. For a 1200 mg dose, this is within the typical maintenance range for adults under 60 years (925-1300 mg daily) 1.
Important Caveats
- Renal function must be monitored: Lithium is almost exclusively renally excreted, and clearance decreases with age 1. The FDA label warns against use in significant renal disease 7
- Drug interactions are critical: NSAIDs, diuretics, and ACE inhibitors can significantly increase lithium levels and toxicity risk 8, 9
- Serum lithium levels should be checked within 1 week of starting or dose changes, then regularly during maintenance
- Toxicity risk increases substantially above 1.5 mEq/L, with early signs including diarrhea, vomiting, drowsiness, and weakness 7
The once-daily bedtime dosing strategy is supported by expert panels and offers practical advantages without compromising efficacy 1, 2.