Re the article (WDDTY vol 15 no 7) ‘The newest brainkillers’ on the harmful side-effects of Ritalin, prescribed for hyperactive children, the British National Formulary, the book which UK GPs prescribe from, also warns that children given Ritalin should also have regular blood tests, as the drug can damage bone marrow and cause blood disorders. Yet, this isn’t done. Parents may be less willing to let their children be prescribed this drug if their children have to endure regular blood tests. – A. Wills, Ruislip, Middlesex