Reaction of Haloperidol with 5-(Hydroxymethyl)-2-furfuraldehyde, an Impurity in Anhydrous Lactose

In the investigation of haloperidol direct compression tablets, using anhydrous lactose as one excipient, a 5–8% loss was encountered on initial assays. Analysis of the lactose by UV, GLC, and mass spectrometry confirmed the presence of 5-(hydroxymethyl)-2-furfuraldehyde. Haloperidol was reacted with 5-(hydroxymethyl)-2-furfuraldehyde and furfural, and conversion to addition compounds resulted. Although both addition compounds were characterized, they could not be isolated from the direct compression tablets.