A 120-pound patient received 108 mg of 2% lidocaine. How many mg of 4% articaine can this patient receive? Provide mathematical formulas to calculate the correct answer

What will be an ideal response?

The MRD for 2% lidocaine is 3.2 mg/lb with a maximum of 500 mg per appointment. The MRD for 4% articaine is 3.2 mg/lb with no determined maximum per appointment. When considering the MRD for more than one drug, the lowest MRD should be used in calculating the second drug's MRD. In this case the MRD is the same for both drugs therefore, 284 mg is the MRD. (3.2 x 120 = 284). Next subtract mg of 2% lidocaine received from MRD (284 – 108 = 176). The patient can receive 176 mg of 4% articaine.