This invention relates to the field of chemical pharmaceutical industry, namely, to pharmaceutical formulations for preparation of prolonged release tablets, in particular, tablets for sublingual application, and to methods of preparation of such formulations. Pharmaceutical formulation comprises 96.0 to 99.8% wt. of the pharmaceutical drug microcapsules, 0.1 to 1% wt. of lubricant, and 0.1 to 3% wt. of water, each microcapsule comprising 96.0 to 99.2% wt. of the pharmaceutical drug and 0.8 to 4% wt. of film-forming substance. Dispersant is also introduced into formulation in the amount of 0.1 to 10% wt. of the total mixture obtained. Method of preparation of the pharmaceutical formulation comprises preparation of microcapsules by deposition of coating of film-forming substance on non-agglomerated particles of pharmaceutical drug, and addition of lubricant and dispersant. In the course of preparation of the microcapsules and/or their intermediate storage moisture content in the coating is brought to concentration not more than 0.5% wt., and prior to addition of lubricant and dispersant microcapsules are moistened to water content of 0.1 to 3% wt. After introduction of lubricant, dispersant is added in the form of fine fraction of said pharmaceutical drug.