# Drug calculations Appendix 10

CALCULATING DOSES FROM PERCENTAGE SOLUTIONS:

Subsequent dilutions can be derived as shown in the table below where each horizontal row contains the same amount of drug.

- The underlying principle of all drug dilutions is that a 100% solution is 1 gram (gm) of drug in 1 ml of volume (a '1 in 1' solution).

- Such a solution contains 100 gm of drug in 100 mls

Subsequent dilutions can be derived as shown in the table below where each horizontal row contains the same amount of drug.

EXAMPLES OF COMMON ICU DRUGS:

- 0.5% bupivacaine contains 5 mg in 1 ml (100 mg in a 20 ml vial)
- 0.2% ropivacaine contains 2 mg in 1 ml (40 mg in a 20 ml vial, 400 mg in a 200 ml bag)
- 2% lignocaine contains 20 mg in 1 ml (100 mg in a 5 ml vial)
- '1 in 1000' adrenaline contains 1 mg in 1 ml or 1000 mcg in 1 ml
- 10% calcium chloride contains 1 gm in 10 ml; this is 6.8 mmol of calcium & 13.6 mmol of chloride
- 49.3% magnesium sulfate contains 493 mg in 1 ml; a single 5 ml vial therefore contains 2.465 g
- 8.4% sodium bicarbonate contains 84 mg in 1 ml; this is 23 mg (1 mmol or 1 mEq) of sodium & 61 mg (1 mmol or 1 mEq) of bicarbonate