Can lithium (lithium carbonate) tablets be cut in half?

Can Lithium Tablets Be Cut in Half?

Lithium carbonate tablets should generally NOT be cut in half unless they are specifically scored tablets designed for splitting, and even then, only immediate-release formulations should be considered—never extended-release or sustained-release preparations.

Critical Safety Considerations

Extended-Release Formulations Must Never Be Split

• Splitting extended-release lithium formulations can result in dangerous overdose due to uncontrolled release of the active component, destroying the controlled-release mechanism 1, 2.
• Sustained-release lithium preparations reach peak plasma concentrations at 4-5 hours (versus 1-2 hours for standard-release), and splitting these destroys this protective pharmacokinetic profile 3.
• Given lithium's narrow therapeutic range—with toxicity beginning at 1.5 mEq/L and serious toxicity at >2.0 mEq/L—any uncontrolled release from splitting extended-release tablets poses significant risk 4.

Immediate-Release Scored Tablets: Proceed with Extreme Caution

• If splitting is absolutely necessary for dose adjustment, only scored immediate-release lithium carbonate tablets should be considered 1.
• Use a proper tablet-splitting device (such as Pilomat®), not scissors, knives, or manual breaking, as splitting devices produce significantly lower mean deviation from theoretical weight and less weight loss 5.
• Manual splitting or use of kitchen implements results in unequal tablet parts and substantial medication loss, which is particularly dangerous for narrow therapeutic index drugs like lithium 5.

Why This Matters for Lithium Specifically

Narrow Therapeutic Window

• Lithium requires precise dosing with therapeutic levels maintained between 0.6-0.8 mmol/L (some sources recommend 0.8-1.2 mmol/L) 3.
• Lithium toxicity is closely related to serum concentrations and can occur at doses close to therapeutic levels 4, 6.
• Large dose deviations from improper splitting can have serious clinical consequences for medications with narrow therapeutic-toxic ranges like lithium 5.

Monitoring Requirements Make Splitting Problematic

• Lithium requires regular monitoring with serum concentrations drawn 12 hours after the last dose 3.
• During acute treatment, levels should be checked twice weekly until stabilized 4.
• Inconsistent dosing from improperly split tablets makes therapeutic monitoring unreliable and potentially dangerous 7, 4.

Better Alternatives to Tablet Splitting

Dose Flexibility Options

• Request lower-strength tablets from the prescriber rather than splitting higher-strength tablets 1.
• Consider liquid lithium formulations if available for more precise dosing 8.
• For elderly patients requiring lower doses (150 mg/day starting dose), use appropriately sized tablets rather than splitting 4.

Special Population Considerations

• Patients with GFR < 60 ml/min/1.73 m² require lower doses and more frequent monitoring—use appropriate tablet strengths rather than splitting 4.
• For patients with GFR < 30 ml/min/1.73 m², a 50% dose reduction is recommended, which should be achieved with lower-strength tablets 4.

Common Pitfalls to Avoid

• Never assume all lithium tablets can be split—check the formulation type and whether tablets are scored 1, 2.
• Do not allow patients to split tablets at home without proper splitting devices and clear instructions 1.
• Approximately 10% of patients who split tablets do so inappropriately with unscored tablets or destroy enteric/modified-release coatings 8.
• The majority of elderly patients are not capable of properly breaking tablets, even when appropriate 1.