WHO guidelines for sampling of pharmaceutical products and related materials discuss on sampling procedure design and implementation. Sampling comprises the operations designed to select a portion of a pharmaceutical product for a defined purpose. 


Sampling may be required for different purposes, such as pre-qualification; acceptance of consignments; batch release testing; in-process control; special controls; inspection for customs clearance, deterioration or adulteration; or for obtaining a retention sample.

The tests to be applied to the sample may include:

  • verifying the identity;
  • performing complete pharmacopoeial or analogous testing; and
  • performing special or specific tests.


The materials to be sampled may belong to the following classes: starting materials for use in the manufacture of finished pharmaceutical products; intermediates in the manufacturing process (e.g. bulk granule); pharmaceutical products (in-process as well as before and after packaging); primary and secondary packaging materials; and cleaning and sanitizing agents, compressed gases and other processing agents.

The sampling procedure should be appropriate to the purpose of sampling, to the type of controls intended to be applied to the samples and to the material to be sampled. 


The procedure should be described in writing. All operations related to sampling should be performed with care, using proper equipment and tools. Any contamination of the sample by dust or other foreign material is liable to jeopardize the validity of the subsequent analyses.


The choice of a sampling plan should always take into consideration the specific objectives of the sampling and the risks and consequences associated with inherent decision errors. 


Sampling facilities should be designed to: prevent contamination of the opened container, the materials and the operator; prevent cross-contamination by other materials, products and the environment; and protect the individual who samples (sampler) during the sampling procedure.


The bibliography at the end of this Annex should be consulted when justifying a sampling plan for a given purpose.


When sampling for regulatory purposes, additional samples for regulatory testing and verification purposes should be provided (e.g. for duplicate testing and parallel testing by different regulatory laboratories and by the consignee of the product). The consignee of the product should be informed that samples have been taken, and should the consignee wish to conduct his/her own testing of the sample taken for regulatory purposes, regulatory authorities should provide a sample to the consignee of the goods. Sampling of products for pre-qualification purposes may follow similar procedures.