Blood donors on medication. Are deferral periods necessary?

Drugs and their metabolites in transfused blood components may cause effects in the recipient. If the treated disorder is not to be regarded as an exclusion criterion from blood donation, donors on medication should be deferred for a period consistent with the drug's pharmacokinetics.

Peak plasma drug concentrations of 3% or less of the therapeutic concentration were regarded to be safe for the recipient of a blood product. For teratogenic drugs a much lower safety level of less than 0.000001% has been proposed. For the calculation of deferral periods, both the type of blood component to be prepared and the drug's pharmacokinetics for a given formulation were considered.

For drugs with known teratogenic risks, we suggest a deferral period of 28 plasma-elimination half-lives. For non-teratogenic drugs, a simple, conservative approach could be based on waiting for five plasma-elimination half-lives, thus reaching the required 3% safety level already in any donor. If, however, the type of blood component to be prepared is also considered, a more differentiated approach appears to be appropriate: for blood components containing 50 ml or less plasma from a single donor, donor medication may be disregarded because of the high dilution in the recipient's plasma volume, whereas for blood components with higher plasma contents (250 ml on average) from a single donor on medication the 3% safety level will be achieved by observing the deferral period of five plasma-elimination half-lives mentioned. A guideline for 191 drugs and drug classes has been elaborated accordingly.