Can fluoxetine (Prozac) capsules be cut in half, or should only scored immediate‑release tablets be split?

Fluoxetine (Prozac) Formulation and Tablet Splitting

Fluoxetine capsules should never be cut or split; only scored immediate-release tablets are appropriate for splitting when dose adjustment is needed.

Why Capsules Cannot Be Split

Capsules contain powder or pellets that cannot be accurately divided, and attempting to open or cut them results in unpredictable dosing, potential loss of medication, and exposure to the drug substance 1. Fluoxetine is available in both capsule and tablet formulations, but the capsule form—which is the most commonly dispensed—is not designed for splitting 2.

When Tablet Splitting Is Appropriate

Only scored immediate-release fluoxetine tablets can be split safely to achieve dose flexibility or cost savings 3, 4. The key requirements are:

• The tablet must be scored (have a dividing line pressed into it by the manufacturer) 3
• It must be an immediate-release formulation, not extended-release or delayed-release 1, 5
• The patient must have adequate manual dexterity and cognitive function to split tablets accurately 1, 4

Evidence Supporting Tablet Splitting for Fluoxetine

Fluoxetine is particularly well-suited for tablet splitting because:

• Its long half-life (4-6 days for the active metabolite) means small variations in daily dose have minimal clinical impact 2, 4
• The long half-life essentially precludes withdrawal phenomena, so minor dose inconsistencies from splitting are clinically insignificant 2
• Therapeutic effects depend on long-term neurotransmitter alterations, not precise daily dosing 4

Research demonstrates that when pill-splitters are used or pharmacies pre-cut tablets, patient satisfaction remains high and compliance is not reduced 4.

Formulations That Must Never Be Split

Extended-release, delayed-release, or enteric-coated formulations must never be split or crushed because:

• Splitting destroys the controlled-release mechanism, causing rapid drug release and potential toxicity 1, 5
• The rate of drug absorption is fundamentally altered, leading to unpredictable peak concentrations and adverse effects 5
• For modified-release formulations, tablets must be swallowed whole to maintain their pharmacokinetic properties 5

Practical Implementation

If dose adjustment is needed:

1. Request scored immediate-release tablets from the prescriber rather than capsules 3
2. Use a tablet splitter device rather than attempting to break tablets by hand, especially for older adults who may struggle with manual splitting 3, 4
3. Have the pharmacy pre-split tablets if the patient has physical limitations affecting their ability to split accurately 4

Common Pitfall to Avoid

Never assume all oral medications can be split—attempting to split capsules, unscored tablets, or extended-release formulations is potentially dangerous and can result in therapeutic failure or toxicity 1, 3. Always verify the specific formulation with the pharmacist before splitting any medication 1.