Single-Dose vs Multi-Dose Vials: How the Closure Choice Differs
A single-dose vial holds one dose and is entered once and then discarded, while a multi-dose vial holds several doses and is entered repeatedly, so the closure requirement differs: a multi-dose vial depends on a rubber stopper that reseals after every needle puncture and a seal that shows clear first-entry tamper evidence, whereas a single-dose vial needs to seal reliably but is only ever opened once. The vial itself is glass in both cases; the meaningful difference is the closure. The stopper must survive repeated punctures and reseal each time on a multi-dose vial, and the aluminium (or aluminium-plastic) seal crimped over it must make first access obvious.
This page compares single-dose and multi-dose vials, explains how the closure choice changes with the number of doses, and sets out which seal family and which nominal size fits each format.
Key takeaways
- A single-dose vial holds one dose, is entered once, and is then discarded; its closure needs to seal reliably but not to reseal. Most emergency and crash-cart drugs are single-dose for exactly this reason.
- A multi-dose vial holds several doses and is entered repeatedly, so its rubber stopper must reseal after each needle puncture and withstand multiple punctures.
- Tamper evidence at first entry matters most on multi-dose vials, because the container is meant to stay in use between doses and users must see that first access has occurred.
- The stopper does the resealing; the aluminium or aluminium-plastic flip-off seal crimped over it holds the stopper in compression and provides the tamper-evident opening.
- Self-sealing and penetrability are functional properties evaluated under USP <382>; the stopper material is qualified under USP <381>.
- Flip-off seals suit multi-dose vials because the flipped button shows first entry while the aluminium crimp stays in place and the stopper reseals for the doses that follow. The FlipTop Optima range covers 13, 20, 28, 32 and 34 mm.
- Full-removal formats suit single-dose vials: the tear-off, tear-down and pull-ring seals take the whole top away in one action, so there is nothing to reclose.
What is the difference between single-dose and multi-dose vials?
A single-dose vial (also called a single-use vial) is designed to be entered one time to deliver a single dose, then discarded, while a multi-dose vial is designed to be entered more than once to deliver several doses over a period of use. The distinction is about how many times the closure is breached, and that changes what the closure has to do.
In both, the container closure system is the glass vial, the rubber stopper, and the aluminium seal crimped over the stopper, working together as one barrier, as set out in vial closure integrity. On a single-dose vial, the stopper is pierced once. On a multi-dose vial, the stopper is pierced several times across the vial’s in-use life, and it must reseal after each withdrawal so the remaining doses stay protected. Multi-dose formulations also commonly include an antimicrobial preservative to control growth over the in-use period, which is a formulation matter, but the closure has to physically support repeated entry.
How the closure choice differs
The closure choice differs mainly in the stopper’s resealing duty and in how obvious first entry needs to be, not in the basic construction, which is a rubber stopper held by a crimped aluminium seal in both cases. The differences are best seen across three properties.
- Resealing. A multi-dose stopper must recover after each needle withdrawal to close the puncture; a single-dose stopper is pierced once, so long-term resealing is not the priority.
- Repeated penetration. A multi-dose stopper must tolerate multiple punctures without coring or losing its seal; a single-dose stopper is penetrated once.
- Tamper evidence. Both should show tamper evidence, but it is especially important on a multi-dose vial, which sits in use between doses, so users must be able to see that the seal was first breached.
Because these duties fall on the stopper and the seal, the vial’s dose format drives the specification of the closure components rather than the glass.
Resealing and repeated puncture
A multi-dose vial relies on a self-sealing elastomeric stopper, typically a butyl rubber stopper, that closes the needle track after each withdrawal so the container does not leak and the remaining doses stay sealed. Self-sealing and penetrability are the functional properties that matter here, and they are evaluated as part of a closure’s functional suitability under USP <382>. A stopper that reseals cleanly and resists coring across repeated punctures is essential to a working multi-dose vial.
A single-dose vial does not place the same demand on the stopper, because it is entered only once. It still needs a stopper that seals and a seal that maintains integrity through storage, but the repeated-puncture and self-sealing performance that defines a multi-dose closure is not the governing requirement. This is why the stopper compound and sometimes the seal format are chosen with the dose count in mind.
Tamper evidence
Tamper evidence is important for every sealed vial, but it is decisive for multi-dose vials, because the container is meant to remain in use between doses and every user needs to see whether first entry has already happened. The aluminium or aluminium-plastic seal provides that evidence. On a flip-off seal, the plastic button is flipped up to reach the stopper, a one-way action that cannot be cleanly reset, so a missing or lifted button signals first entry. On a tear-off or tear-down seal, the torn or missing metal is the evidence.
For a single-dose vial, tamper evidence still matters, but because the vial is used and discarded in one action, the seal is breached and the vial finished in a single step. For a multi-dose vial, the seal has to clearly separate the untouched state from the in-use state, which is one reason flip-off seals are common on multi-dose injectables. The mechanics of the tamper-evident opening are compared in flip-off vs tear-off seals.
Single-dose vs multi-dose: the comparison
The closure requirement scales with the number of doses: a single-dose vial needs a reliable one-time seal, and a multi-dose vial needs a resealing, multi-puncture stopper plus clear first-entry tamper evidence.
| Aspect | Single-dose vial | Multi-dose vial |
|---|---|---|
| Doses per vial | One | Several |
| Times the stopper is pierced | Once | Multiple |
| Resealing requirement | Low (single entry) | High (must reseal each time) |
| Stopper duty | Seal and be pierced once | Self-seal and resist coring over repeated punctures |
| First-entry tamper evidence | Useful | Critical (vial stays in use between doses) |
| Common seal format | Tear-off, tear-down, pull-ring, or flip-off | Flip-off (clear first-entry evidence) |
| Preservative in formulation | Often none | Often an antimicrobial preservative |
The table shows the closure, not the glass, is what changes. The same crimped-aluminium-over-stopper construction serves both, tuned for a single entry or for repeated, resealing entries.
Which seal family suits each format
A multi-dose vial is the classic case for a flip-off seal, because the button flips, the aluminium crimp stays on the vial, and the stopper reseals after each withdrawal; a single-dose vial leans towards tear-off and tear-down, where the whole top comes away in one action and nothing is meant to be reclosed. The distinction is mechanical, not commercial.
On a flip-off seal, only the moulded polypropylene button moves. The aluminium shell remains rolled under the vial neck flange, so the stopper stays compressed against the glass and the needle track is the only opening in the barrier. That is exactly what a vial re-entered over a period of use needs. On a tear-off, tear-down or pull-ring seal, the aluminium itself is removed: the tear-off tears along a perforation, the tear-down is opened at the polypropylene disc then pulled and rotated anticlockwise so the whole seal lifts off, and the pull-ring detaches once the disc is pulled. Once the aluminium is off, the stopper is no longer held, so the vial cannot be returned to storage.
| Seal family | Sizes available | Opening action | Which vial format it suits |
|---|---|---|---|
| FlipTop Optima flip-off | 13, 20, 28, 32, 34 mm | Polypropylene button flips up; aluminium crimp stays | Multi-dose, and single-dose where a small needle port is preferred |
| Tear-off, all-aluminium | 13, 20, 32 mm | Metal tears along a perforation, whole top removed | Single-dose |
| FlipTop Tear-Down | 13, 20, 32 mm | Disc opened, then pulled and rotated anticlockwise, whole seal off | Single-dose, oral dosing |
| FlipTop Pull Ring | 20, 32 mm | Aluminium ring pulled, whole seal detaches | Single-dose, oral dosing |
Size and family are separate decisions. The size is fixed by the vial neck finish, which follows ISO 8362-1, and by the stopper of the same nominal diameter; the family is chosen for how the vial is used. Working through both in order is covered in how to choose a vial cap size.
Specifications by size and family
Controlled dimensions for the seal families that serve each format, taken from the Autofits engineering drawings. Match the nominal size to the vial neck and stopper before comparing anything else.
FlipTop Optima flip-off, the default for multi-dose:
| Size | Inner Ø aluminium (D1) | Outer Ø disc (D2) | Total seal height | Aluminium thickness | Bridges |
|---|---|---|---|---|---|
| 13 mm | 13.36 mm (min) | 14.99 mm (max) | 7.62–8.38 mm | 0.16–0.20 mm | 6 taper |
| 20 mm | 20.22 mm (min) | 23.14 mm (max) | 9.02–9.91 mm | 0.16–0.20 mm | 6 taper |
| 28 mm | 27.60–28.20 mm | 30.10–31.10 mm | 11.06–12.06 mm | 0.17–0.23 mm | 8 |
| 32 mm | 32.10–32.90 mm | 35.50–36.50 mm | 14.30–15.50 mm | 0.21–0.25 mm | 12 taper |
| 34 mm | 33.60–34.00 mm | 35.50–36.50 mm | 15.00–16.00 mm | 0.20–0.25 mm | 8 taper |
Maximum opening force is 30 N at 13 mm, 35 N at 20 mm, 35 N at 28 mm and 65 N at 32 mm, varying with the number of bridges in the design.
Full-removal families, the usual choice for single-dose and oral presentations:
| Family and size | Inner Ø aluminium (D1) | Second Ø (disc or perforation) | Total height | Aluminium thickness | Bridges or fins |
|---|---|---|---|---|---|
| Tear-off 13 mm (all-aluminium) | 13.20–13.60 mm | On request | 6.90–7.70 mm | On request | 2 |
| Tear-off 20 mm (all-aluminium) | 20.00–20.60 mm | 9.70–10.50 mm (perforation) | 7.40–8.00 mm | 0.16–0.20 mm | 2 |
| Tear-off 32 mm (all-aluminium) | 32.40–32.60 mm | 17.80–18.20 mm (perforation) | 13.00–13.60 mm | On request | On request |
| Tear-Down 13 mm (aluminium-plastic) | 13.30–13.50 mm | 14.80–15.40 mm (disc) | 6.80–8.30 mm | 0.18–0.22 mm | Bridge |
| Tear-Down 20 mm (aluminium-plastic) | 20.00–20.60 mm | 22.00–23.00 mm (disc) | 8.80–9.80 mm (assembled) | On request | Bridge |
| Tear-Down 20 mm (all-aluminium) | 20.50–20.70 mm | 12.90–13.20 mm (perforation) | 7.50–8.50 mm | 0.18–0.22 mm | 2 taper |
| Tear-Down 32 mm (aluminium-plastic, flower) | 32.40–33.15 mm | 35.70–36.70 mm (disc) | 14.30–15.30 mm | 0.20–0.26 mm | 8 fins |
| Pull Ring 20 mm | 20.00–20.60 mm | 22.00–23.00 mm (disc) | 9.00–10.00 mm | 0.18–0.22 mm | 6 taper bridges |
| Pull Ring 32 mm | 32.15–32.40 mm | 36.20–36.60 mm (disc) | 14.30–15.30 mm | 0.20–0.26 mm | 8 fins (flower) |
Aluminium-plastic combination caps are made to ISO 8362-6; all-aluminium seals relate to ISO 8362-3. Every size can be reached from the by-size hub, including 13 mm, 20 mm and 32 mm.
Forms of supply, packing and shelf life
Both formats are served from the same three forms of supply. Regular is the non-sterile form, for lines that wash and sterilise incoming components themselves. Ready-to-Use seals are washed to remove particles, assembled in an ISO Class 8 cleanroom, double-lacquered, gamma or ETO sterilized and supplied double-bagged, so they pass into an aseptic area without further processing. Ready-to-Sterilize seals are supplied clean and bagged for the customer’s own validated cycle. Shelf life is 3.5 years before capping for non-irradiated seals, plus 5 years after capping, and 2 years before capping for Ready-to-Use.
Standard packing is 15,000 per box at 13 mm (5,000 in each of three bags), 6,000 at 20 mm (2,000 in each of two bags), 3,000 at 28 mm (1,500 in each of two bags) and 1,400 at 32 mm (700 in each of two bags), in a 420 × 270 × 320 mm shipper. Tyvek bagging is available. To specify a closure for a single-dose or multi-dose presentation, send the vial neck finish, the stopper reference, the nominal size and the form of supply required through the contact page; colours are available matte or glossy, customised to requirement.
Which seal fits which vial at Autofits
Autofits manufactures the aluminium and aluminium-plastic seals that crimp over the rubber stopper on both single-dose and multi-dose vials; it does not make the stopper, which is the component that does the resealing. For multi-dose injectables, where clear first-entry tamper evidence suits a vial that stays in use, the FlipTop Optima flip-off seals provide a flipped-button opening while the aluminium crimp keeps the stopper sealed for later doses, and the Button design carries intrinsic tamper evidence through a 12-stem flower under the button disc. For single-dose and oral presentations that call for fast, full removal, the tear-down seals and the pull-ring seals take the whole top away, and the pull-ring versus tear-down comparison sets out the difference in the opening action. Whichever seal is chosen, the aluminium skirt crimps over the stopper and vial neck to hold the container closure integrity; the stopper’s self-sealing performance across punctures is a property of the stopper compound, qualified under USP <382>. Autofits produces these seals under an ISO 15378:2017 quality system in a 75,000 sq ft Nashik facility with an ISO Class 8 cleanroom and 100% high-speed camera inspection.
The single-dose versus multi-dose split maps closely onto drug category. Multi-dose is the norm on insulin and hormone vials, multidose vaccine presentations and large-format veterinary vials, which is where 20 mm and 32 mm flip-off seals concentrate. Single-dose dominates wherever a second entry is unacceptable, which covers ophthalmic preparations and most cytotoxic oncology fills, and where 13 mm sizes and full-removal formats are common.
Frequently asked questions
What is the difference between a single-dose and a multi-dose vial?
A single-dose vial holds one dose, is entered once, and is then discarded. A multi-dose vial holds several doses and is entered repeatedly over a period of use, so its rubber stopper must reseal after each needle puncture and its seal must show clear first-entry tamper evidence. The vial is glass in both cases; the difference is what the closure has to do.
Why does a multi-dose vial need a self-sealing stopper?
Because a multi-dose vial is pierced several times, the stopper must close the needle track after each withdrawal so the container does not leak and the remaining doses stay sealed and protected. This self-sealing and multi-puncture performance is a functional property of the stopper, evaluated under USP <382>. A single-dose vial is pierced once, so it does not place the same repeated-resealing demand on the stopper.
Does the aluminium seal reseal a multi-dose vial?
No. The resealing is done by the rubber stopper, which recovers to close each needle puncture. The aluminium or aluminium-plastic seal crimps over the stopper to hold it compressed against the glass and to provide tamper-evident opening; it does not itself reseal. On a flip-off seal, the button is flipped once to reach the stopper and cannot be reset, which signals first entry.
Which seal is best for a multi-dose vial?
A flip-off (aluminium-plastic) seal is the usual choice for a multi-dose injectable vial, because flipping the polypropylene button is a one-way action that clearly shows first entry, while the aluminium crimp stays rolled under the neck flange and keeps the stopper sealed for the doses that follow. The FlipTop Optima flip-off range covers 13, 20, 28, 32 and 34 mm. The stopper underneath must be a self-sealing elastomer rated for repeated puncture.
Which seal suits a single-dose vial?
Single-dose vials suit full-removal formats, because nothing needs to be reclosed after the one entry. All-aluminium tear-off seals are made in 13, 20 and 32 mm and tear along a perforation. FlipTop Tear-Down seals are made in 13, 20 and 32 mm and come off completely when the disc is pulled and rotated anticlockwise. Pull-ring seals, in 20 and 32 mm, detach once the aluminium ring is pulled. A flip-off seal is also used on single-dose vials where a small needle port is preferred.
Is tamper evidence more important on single-dose or multi-dose vials?
Tamper evidence matters on both, but it is more critical on multi-dose vials, because the container stays in use between doses and each user must be able to see whether first entry has already occurred. A single-dose vial is breached and finished in one action, so the untouched-versus-used distinction is less of an ongoing concern than on a vial that is stored and re-entered.
Related reading
- FlipTop Optima flip-off seals, all five sizes
- Tear-down seals for full removal
- Pull-ring seals
- Browse seals by size
- Flip-off vs tear-off seals compared
- USP <382>: elastomeric component functional suitability
Sources
- USP-NF: General Chapter <382>, Elastomeric Component Functional Suitability in Parenteral Product Packaging/Delivery Systems (https://www.usp.org/)
- USP-NF: General Chapter <381>, Elastomeric Components in Injectable Pharmaceutical Product Packaging/Delivery Systems (https://www.usp.org/)
- ISO: ISO 8362-2, Injection containers and accessories, Part 2: Closures for injection vials (https://www.iso.org/)
- ISO: ISO 8362-6:2010, Injection containers and accessories, Part 6: Caps made of aluminium-plastics combinations for injection vials (https://www.iso.org/)
- US FDA: Safe use of single-dose and multi-dose vials (https://www.cdc.gov/)
- Autofits FlipTop Seals dossier and engineering drawings (working/spec-sheets/)
*Last updated: 2026-08-18. This article is general technical information, not clinical or regulatory advice; confirm current standard editions, formulation requirements, and product specifications with the issuing bodies and your supplier.*
