This invention provides for a pharmaceutical or veterinary paste formulation comprising: an effective amount of a therapeutic agent; fumed silica; an absorbent and a viscosity modifier; optionally a hydrophilic carrier and optionally, a colorant, stabilizer, surfactant, or preservative and methods of preparing these formulations. This invention also provides for, inter alia, oral homogeneous veterinary pastes for the treating, controlling and preventing of endo- and ectoparasite infections in warm-blooded animals, such as birds, horses and household pets.