A plastic closure device for a container for parenteral pharmaceutical products having a bottle provided with a neck is provided. The plastic closure device has an outer cap with tearable weakenings to allow tear-off removal of the outer cap and an inner cage provided with a head having a central opening. A skirt ending in a lower edge extends below the central opening. Retaining elements for permanent snap engagement on the neck of the bottle are provided at the lower edge. The outer cap is snap-engaged under the lower edge of the inner cage by coupling elements. The plastic closure device guarantees authenticity of the container and its tightness even in the event of tampering attempts.