The diamond standard of CD prevention technology is interception detection technology. Essentially with every shipment you need to include a device that has secret information in volatile memory and which is hooked up to a photovoltaic cell. It needs to be constructed such that if light hits the photovoltaic cell, the secret information is wiped. Get the package sent to a PMB registered with a fake ID, and prior to picking the package up query the included device for the secret information (it could use a zero knowledge proof of knowledge). If it has the secret information that means the photovoltaic cell was never triggered, which means the package was never opened (or it was opened in a darkroom). If it doesn't have the secret information, that means the photovoltaic cell was triggered, which means that somebody opened the package between you and the vendor. You could also have it test for pressure or for the presence of oxygen, and vacuum seal the device with the drugs.