Question

Case #1 S.P. is a 58-year-old man who is sitting at home watching television with his wife when he develops confusion, nausea, severe headache, and right arm weakness. His wife immediately calls for an ambulance and by the time paramedics arrive, S.P. is slumped in his chair and unresponsive. S.P has a past medical history significant for poorly controlled hypertension, atrial fibrillation, and osteoarthritis. He takes lisinopril, warfarin and acetaminophen. Upon arrival to emergency in the hospital, the attending physician provided medications for immediate attention. He then sends a prescription of lisinopril to the pharmacy to be filled for the patient to take home. The pharmacy has a 200 mL of 15% stock solution of lisinopril. The pharmacy Technician added water to the stock solution in order to dilute the solution but could not remember the volume of water that he added to the stock solution. Upon receiving the prescription from the physician, the pharmacist took 40 ml of this diluted stock solution, added another 100 mL of water to it to further dilute it and determined that the strength of the final solution is 1:400. Calculate how many milliliters of water were added to the initial stock solution by the pharmacy technician.

Answer 1

Case 1#

Step 1:

By using the equation,

C₁ / V₁ = C₂ / V₂

Concentration₁ = 200mL

Volume₁ = X

Concentration₂ = 40mL

Volume₂ = 100mL

Step 2:

By substituting on the above equation,

200 / X = 40 / 100

40X = 20000

X = 500mL

500mL of water added to the initial stock solution of lisnopril by pharmacy technician.