Physical Characteristics of Sixteen Non-Prescription Medications: Specific Gravity, Ph, Surface Tension, and Rheological Characteristics

The physical characteristics of Over-The-Counter (OTC) medications serve as important parameters for the compounding pharmacist in order to prepare the prescription tailored to the patient's needs. In this study, three containers of sixteen different OTC products were tested for their pH, surface tension, specific gravity, and their rheological behavior. All measurements were recorded at room temperature and in triplicates. The specific gravity was determined by the use of two different instruments (pycnometer and Densito 30 PX), and the results obtained from both methods were in good agreement with each other. All products were found to be denser than water except Witch Hazel USP Hamamelis Water which had a specific gravity of 0.98. Tustin DM cough syrup had the highest specific gravity of 1.26.pH of all products was found to be acidic except for DIgel Antacid and Antigay which showed basic pH of 8.07. Tustin DM cough syrup was found to be the most acidic with an average pH of 2.65. All products had an apparent surface tension value similar to or less than that of water. Pediatric Electrolyte had surface tension similar to that of water while Tustin DM Cough Syrup had the smallest value for surface tension (45.74 dynes/cm).Viscosities of all Newtonian and non-Newtonian products were measured by an Ostwald viscometer and a remoter, respectively, except for DI-gel Antacid and Anti gas was measured by a Brookfield Viscometer. Most of the Newtonian products had viscosity similar to water, except for Allergy Liquid, Children's Day Time Cough and Cold Syrup, and Tustin DM Cough syrup which showed viscosity values of 3.23, 27.02, and 27.18 cPs, respectively. Children's Day Time Cough and Cold Syrup had the highest kinematic viscosity of 22.41cSt, whereas Podia One Oral Therapy Rehydration had the lowest value of 1.02cSt. DI-gel Antacid and Antigay was found to exhibit thyrotrophic (pseudo plastic) behavior when subjected to stress. Triple Antibiotic Ointment and the toothpastes were tested using a remoter. Rheological parameters, namely compliance factor (Jo) and ground viscosity (?o), were determined from their respective rheograms. Triple Antibiotic Ointment was found with smallest compliance factor (Jo) value of 5.7 x 10-5 Pa-1, whereas the highest value was seen with Crest Toothpaste (3.12 x 10-3 Pa-1). The viscosity value of Max Block After sun Gel was found to be the highest (2.9 x 105Pa.s). The information obtained may serve as a resource for pharmacists while compounding medications for their patients.