1. Tamper-evident: These bottles usually have a secure child-resistant cap, which makes it difficult for children to open the bottle. The tamper-evident feature is another safety aspect that assures the consumer that the bottle has not been opened or tampered with.

2. Light-resistant: Many medications can be harmed by exposure to light. Thus, these plastic bottles are designed to be opaque or have dark color to prevent light from penetrating the bottle and damaging the medication.

3. Durable: The plastic material of these bottles is very strong and resistant to breakage, ensuring that the medication is not damaged during transport or storage.

4. Airtight: These bottles are sealed airtight to maintain the freshness and potency of the medication. This is especially important for pills that are sensitive to air or moisture.

5. Recyclable: The majority of plastic bottles containing medication are made with recyclable materials, which makes them environmentally friendly.

Overall, the design of plastic bottles containing pills is aimed at protecting the consumer and ensuring the medication's quality and potency.