Drugs which increase the risk of vitamin D deficiency

For many drugs the likelihood of impacting vitamin D levels is difficult to quantify or based on limited evidence. This search strategy aims to include drugs where there is a weight of credible evidence that they commonly reduce vitamin D levels. A conclusion for each medication was arrived at after consulting multiple sources such including, BNF, Summary of Product Characteristics, relevant published literature. Drug classes were not included where they are known to be almost exclusively prescribed in secondary care, such as highly active antiretroviral agents or chemotherapeutic agents.

Search terms are defined as follows: Anticonvulsants: Carbamazepine, Phenytoin/Fosphenytoin, Phenobarbital, Primidone, Valproate. Other: Colestyramine, Orlistat, Rifampicin.

Inclusion criteria for codes: Codes which when applied in clinical records, are expected to indicate the prescription of a vitamin D–depleting medication in >99% of cases.

Exclusion criteria for codes: Codes which when applied in clinical records, are expected to indicate the prescription of a vitamin D–depleting medication in <99% of cases.