Drug, alcohol and other substance (e.g. solvent) misuse is everyone's concern. It damages health, causes absenteeism and reduced productivity.
In the context of work, not only does it damage the misuser's health, but it can cost employers through absenteeism and reduced productivity. It may also increase the risk of accidents. Employers should adopt a substance abuse policy, in consultation with their staff. This policy should aim to support affected employees rather than punish them, though your policy should note that possession or dealing in drugs at work will be reported immediately to the Police. If an employee admits to being a drug user, your policy should seek to help them rather than lead simply to dismissing them.
Some employers have decided to adopt drug screening as part of their drug policy. If you think you want to do the same, think very carefully about what you want screening to do, and what you will do with the information it generates. It is also important to consider the drug testing process itself including the type of testing, how the sample is collected and the security of the sample from contamination.