Tall man letters are used for drugs which:

Several studies have shown that highlighting sections of drug names using tall man (mixed case) letters can help distinguish similar drug names, making them less prone to mix-ups. The tall man letters are used to help draw attention to the dissimilarities in drug names. For instance Celexa would be written as CeleXA to avoid confusion with CeleBREX. The Institute for Safe Medical Practices (ISMP), the FDA, and the Joint Commission promote the use of tall man letters as one method of reducing confusion between similar drug names.