Pharmaceutical aluminum foil, which is commonly used to package pharmaceuticals, is usually not itself waterproof. Vendar, it has a certain degree of resistance to water and other environmental factors. This is due to the special structure of medicinal aluminum foil

Moisture Barrier: Pharmaceutical foils are usually designed with a moisture barrier or coating. This barrier helps prevent moisture, water vapor, and other liquids from penetrating the foil and coming into contact with the drug product inside. This is very important to maintain the integrity and effectiveness of the drug.

Sealing: Pharmaceutical aluminum foil is often used to create airtight packaging for individual doses or units of pharmaceuticals. The packaging process includes heat sealing the foil to create a tight, tamper-proof seal. This sealing process also helps keep moisture out.

Protection: While medicinal foil is not completely waterproof like plastic or rubber materials, it can provide significant protection against environmental elements, including moisture and humidity. This protection is critical to maintaining the stability and shelf life of pharmaceutical products.

Outer packaging: In many cases, pharmaceutical grade aluminum foil is used as an inner layer of packaging, which is then further encapsulated in an outer packaging, such as a blister pack or box. This outer wrap can provide an extra layer of protection from water exposure.

Although pharmaceutical grade aluminum foil has a certain degree of moisture resistance, it is not completely impermeable. Excessive exposure to water or prolonged exposure to high humidity can compromise the integrity of the package and the quality of the drug product.