Tamper-evident packaging: proving first opening
A tamper-evident cap does not stop anyone from opening a bottle. It does something else: it proves the bottle has never been opened. That proof rests on a few slender plastic bridges, and getting them right is decided in the mould.
By Tecmom editorial team · 3 min read
Chicago, autumn 1982
In the autumn of 1982, seven people died in the Chicago area after taking Tylenol capsules laced with cyanide. The bottles had been tampered with and put back on store shelves. Nothing showed that they had been opened.
The same year, the US FDA required over-the-counter medicines to come in packaging that betrays any opening. The rule now sits in 21 CFR 211.132: a tamper-evident package has one or more indicators or barriers to entry which, if breached or missing, give consumers visible evidence that tampering has occurred.
Proof, not prevention
The name can mislead: a tamper-evident cap opens like any other. It does not resist opening; it makes opening visible and irreversible. A pharmacist or patient who finds the indicator broken knows the bottle has been opened before.
That is what sets it apart from a child-resistant closure, which must resist a young child while remaining usable by an adult, according to the tests of ISO 8317. One proves, the other holds back. A single closure can do both.
A band, some bridges and a bead
On a screw cap, the most common indicator is a tamper-evident band moulded below the cap skirt. It has nothing to do with the bottle neck finish, which refers to the diameter of the neck.
The band is held to the cap by thin frangible bridges. On first unscrewing, it catches under a ridge on the neck, the bead, and the bridges give way: the band stays on the neck, separated from the cap. The gap shows at a glance, and nothing can undo it.
The whole difficulty lies in those bridges. Too thin, and they break during capping, so the bottle leaves the line with its indicator already broken. Too thick, and they resist opening. Their cross-section, like the ridge that catches the band, comes out of the injection mould finished, with no rework: everything is decided when the tooling is designed. That is the trade in the company's name, Technologies Moules et Matrices. See our expertise.
What the rules say
In the United States, 21 CFR 211.132 covers over-the-counter drugs. It requires tamper-evident packaging and a statement on the label that tells patients which indicator is used.
In the European Union, since 9 February 2019, prescription medicines for human use carry an anti-tampering device. Delegated Regulation (EU) 2016/161 defines it as the safety feature that allows verification of whether the packaging has been tampered with. It goes on the outer packaging, or on the immediate packaging when there is none.
The ISO 21976:2018 standard describes tamper verification features for medicinal product packaging. Breakable closures form one category, alongside glued folding boxes, sealing labels and film wrappers.
Tamper-evident caps in the Tecmom range
The Tecmom catalogue includes four caps and one pill container fitted with a tamper-evident band: a 20 mm cap, a 52 mm cap in white and in blue, a PP28 tamper-evident cap for 28 mm neck finishes, and a 36 ml tamper-evident pill container with a 34 mm neck finish.
They are injection-moulded in Bouskoura, Morocco, in moulds designed by Tecmom, under ISO 9001 and ISO 15378 certifications. See quality. For any given bottle, everything starts at the neck: its finish decides which cap closes it, and its bead decides which band catches on it.
A tamper-evident cap does not protect the contents; it protects the trust placed in them. A few plastic bridges, drawn in the steel of the mould, are enough to tell pharmacist and patient alike: nobody has opened this bottle before you.
Glossary
- Tamper-evident band
- A ring moulded below a cap skirt that separates on first opening and keeps the evidence.
- Frangible bridge
- A thin plastic link between the band and the cap, designed to break on first unscrewing.
- Bead
- A ring-shaped ridge on the neck that the band catches under when the cap is opened.
- Primary packaging
- Packaging in direct contact with the medicine.
- Injection moulding
- A process that forces molten plastic into a closed mould under pressure; fine details come out finished.