Several technical factors related to penicillin G intramuscular injection can affect its bioavailability and hence reduce the efficacy of rheumatic fever prevention program. When small amount of diluent is used, the powder is not completely dissolved and the thick suspension frequently causes obstruction of injection needle. The study aimed to characterize the solid-state properties of solid dispersion systems of benzathine penicillin G (BPG) prepared with hydrophilic carriers by applying solvent evaporation method. The results of spectroscopic studies; Fourier transform-infra red (FTIR), Nuclear Magnetic Spectroscopy (1HNMR) and Differential Scanning Calorimetry (DSC) revealed no chemical interaction between the drug and carriers. No significant changes in drug crystalline state were observed by X-ray diffraction and Scanning Electron Microscope (SEM) studies, even with using amorphous carriers; polyvinyl pyrrolidone (PVP-K30) and hydroxypropyl methylcellulose (HPMC). All the prepared solid dispersions demonstrated 76-93% yield and % drug content dependent on the polymer type and concentration. The hydrophilic polymers demonstrated potential effect on improving the flowability, wettability and dissolution characters of the drug. The results revealed that it is possible to enhance the dissolution rate of BPG (hydrophobic drug) by increasing the surface area of the drug adsorbed on the surface of hydrophilic polymer by solid dispersion method. Finally, solid dispersion BPG: PEG 4000 at ratio 50:50 gave uniform flowability of the powder (around 30), wettability (12 min) and faster dissolution rates among all the formulations. Thus, it was selected as the best formulation in this study
