A blister pack is a common packaging method consisting of pre-formed plastic or aluminum cavities that house individual doses of medication. This unit-of-use packaging is widely utilized across the pharmaceutical industry for oral solids like tablets and capsules. The design provides a sealed, protective environment for each dose, ensuring the medicine remains safe and effective until the patient uses it. This packaging has become the standard for safeguarding drug products and supporting patient health.
Anatomy of a Blister Pack
A typical blister pack is constructed from two primary components: the thermoformed plastic cavity and the lidding material. The plastic cavity, often called the blister, is formed through heat processing sheets of material like polyvinyl chloride (PVC) into distinct pockets customized to fit the specific tablet or capsule.
The lidding material is typically a tight seal of aluminum foil, paper, or a plastic laminate. This lidding is tightly bonded to the plastic sheet after the medication is placed into the pockets. The seal forms a closed space around each pill, isolating it from the external environment. For medications requiring higher protection, the PVC may be coated with polyvinylidene chloride (PVDC) to enhance its barrier properties.
Primary Functions in Medication Protection
The primary purpose of the blister pack is to maintain the chemical stability and efficacy of the drug product. Packaging materials are chosen to act as a barrier against environmental factors that cause degradation, such as moisture, oxygen, and light. Aluminum foil, commonly used for the lidding, offers excellent protection because it provides a total barrier against these external elements.
When standard PVC is used, its barrier effect against water vapor and oxygen is limited. For highly sensitive or hygroscopic drugs, manufacturers often use PVDC-coated PVC films or specialized Alu-Alu blister packs. PVDC significantly increases the barrier against oxygen and water vapor transmission, helping to extend the medication’s shelf life. The individual sealing of each dose ensures that removing one tablet does not compromise the protection of the remaining pills.
Another function is providing clear tamper evidence for the consumer. Because each tablet is sealed in its own pocket, any attempt to access the medication before use results in a visible break or tear in the lidding material. This immediate visual cue assures the patient of the product’s integrity before ingestion.
Supporting Patient Dosing and Safety
Blister packs simplify the process of correct medication usage through unit-dose delivery. Each pocket contains a single, prescribed dose, which helps prevent patients from accidentally taking the wrong amount of medicine. This design also serves as a visual record, allowing patients to easily check if they have taken their scheduled dose or if a dose has been missed.
Many blister packs are designed as “calendar packs,” printed with days of the week or dates corresponding to the doses. This feature acts as a memory aid, prompting patients to follow the prescribed dosing schedule and significantly improving medication adherence. Patients using unit-dose calendar packaging are more likely to comply with their regimens compared to those using traditional pill bottles. This improved adherence is beneficial for long-term treatments where patient forgetfulness is a common cause of unintentional nonadherence.
For safety, some blister packs incorporate child-resistant features required for certain medications. These designs make it deliberately difficult for young children to access the contents. The child-resistant mechanisms often require specific, coordinated actions, such as a peel-push or tear-open sequence. This design ensures that while the packaging remains relatively easy for adults to open, it provides a strong barrier against accidental ingestion by curious children.