Does zonisamide expire?
The printed date covers the sealed pack. Once zonisamide is opened, mixed or diluted, its label sets a second and usually much shorter limit — quoted below, per product.
Shortest limit on any zonisamide label: 30 days
“Discard unused portion of ZONISADE 30 days after first opening of the bottle.”
That applies to the product it is printed on, not to every form of zonisamide — check which one you have against the list below.
What the labels say
“Discard unused portion of ZONISADE 30 days after first opening of the bottle.”
On the label for ZONISADE · DailyMed
“Discard unused portion of ZONISADE 30 days after first opening the bottle.”
On the label for ZONISADE · DailyMed
“Instruct patients to shake ZONISADE well and discard any unused portion after 30 days of opening the bottle [see Dosage and Administration ( 2.”
On the label for ZONISADE · DailyMed
How the label says to keep zonisamide
Storage is the other half of the question: the stability behind any date assumes these conditions, and a medicine kept outside them ages faster than the calendar says.
- “Store at 20 o C to 25 o C (68 o F to 77 o F) [see USP Controlled Room Temperature].”
- “Keep in dry place and protect from light.”
- “Store at 25°C (77°F), excursions permitted to 15-30°C (59-86°F) [see USP Controlled Room Temperature], in a dry place and protected from light.”
- “Store at 20oC to 25oC (68oF to 77oF) [see USP Controlled Room Temperature].”
- “Store at 20°C to 25°C (68°F to 77°F) [see USP Controlled Room Temperature], in a dry place and protected from light.”
- “Store at 25°C (77°F), excursions permitted to 15°-30°C (59°-86°F) [see USP Controlled Room Temperature], in a dry place and protected from light.”
- “Store at 25°C (77°F), excursions permitted to 15° C to 30°C (59°F to 86°F).”
- “Store in a dry place and protect from light.”
Frequently asked questions
Does zonisamide expire?
Two different clocks apply and only one of them is the printed date. The date on a sealed pack is the manufacturer's guarantee for the unopened product. Once it is opened, mixed or diluted, the label imposes its own limit — as tight as 30 days on some zonisamide products, and that is the number quoted on this page.
Can I still use zonisamide after the date on the box?
This page cannot tell you that, and nor can any page. The FDA's own shelf-life programme found 88% of tested lots stayed within specification at least a year past expiry — and concluded in the same breath that lot-to-lot variation means this can only be confirmed by testing each lot. What you can check at home is the in-use limit above and whether the product has been stored as the label requires. Ask a pharmacist about a specific pack; they will also dispose of what you no longer need.
Why do different zonisamide products have different limits?
Because they are different formulations. A suspension that gets mixed with water, a pen that gets carried at room temperature, and a sealed tablet do not behave alike, so each manufacturer's label sets its own limit and each is shown here with the product it belongs to. We never merge them into one number for the molecule.
More on zonisamide
Quoted from FDA labels for reference, not medical advice, and not a suggestion to use anything past its limit. If you are unsure whether a pack is still good, a pharmacist can tell you and can dispose of it safely.