A blister pack is the foil-and-plastic card that holds your medicine in individual sealed pockets. One tablet per cavity, the rest stay protected until you press the next one through. It's the most common pharmaceutical packaging format in the world for solid oral medicines, and there's more engineering inside that simple card than most people realize.
What sits inside the cavity
Two materials make a blister pack. The forming film at the bottom shapes the cavities. The lidding foil seals them shut. The patient pushes the tablet through the foil to release the dose.
The forming film is plastic or aluminum laminate. PVC for cheap, stable formulations. PVDC-coated PVC when you need a better moisture barrier. ACLAR when you also need a light barrier. Cold-formed aluminum (Alu-Alu) when the API is so sensitive that even the small amount of moisture passing through plastic over two years of shelf life would degrade it.
The lidding foil is almost always aluminum, sometimes laminated with paper or plastic. Coated on the inside with a heat-seal or cold-seal adhesive. The print on top carries the brand, the dose, and often a day-of-the-week label.
Thermoformed vs cold-formed blisters
Two ways to shape the cavity. Thermoforming heats the plastic film and presses it into a mold. Fast, cheap, works for most solid orals. Cold forming uses pressure alone to shape an aluminum laminate, no heat needed. Slower and more expensive, but it produces the highest barrier protection in pharma packaging. If your stability study screams humidity, you go cold formed.
Cold-seal blister wallets
A separate category. Instead of a blister card sitting inside a folded carton, the blister is bonded directly to a paperboard wallet. The bonding uses cold-seal adhesive, no heat. That's relevant when the API itself is heat-sensitive, like biologics or hormone therapies, because the assembly step never warms the product.
The other reason to use a wallet is the patient. The wallet becomes a printable surface where you lay out a calendar, color-code the dosing schedule, or include child-resistant features. Cold seal blister wallets are what we run for most of our pharma customers.
What blister packs do for the patient
Three things, mainly. First, dose tracking: a glance tells the patient whether they took their Wednesday tablet. Second, tamper evidence: a torn foil is obvious. Third, individual protection: the dose you take next month is still sealed today, no air exchange between cavities.
For chronic medications and complex regimens, that's the difference between adherence and non-adherence. Calendar-layout wallets lift compliance roughly 30% in published studies, which translates into measurable clinical outcomes.
Where companies pick the wrong blister
Two common mistakes. The first: assuming PVC is fine because the API "isn't that sensitive", then watching the stability data fail in month nine. Always run the full study before locking in the material.
The second: forgetting about the patient. A pediatric API in a pack a four-year-old can open. A geriatric API in a pack a 78-year-old can't open. Both happen. Both are caught in patient-acceptance testing if you do it.
How we help
We've been pairing pharmaceutical APIs to blister formats since 1996. If you're spec'ing a new launch and want a second opinion before signing off, send us the stability data and patient profile. We'll come back with two or three blister formats that match. Or ask for samples if you want to feel the difference between PVC and Alu-Alu in your hand.
Request a free sample now!
