# Dose to gtt/min Calculator

## Dose to gtt/min Formula

First convert units if necessary. Available and ordered units must match. This is true with lidocaine and diltiazem but not so with nitroglycerin and dopamine. Available units in nitrogycerin must be converted from milligrams to micrograms:

A × 1,000 mcg

- A = Dose available

Next, use the dose formula to calculate rate.

- O = Dose ordered
- V = Volume of dose available
- C = Calibration
- A = Dose available

## Dose/kg to gtt/min Formula

First, convert available units to match ordered units if necessary. Next, use the dose formula to calculate rate.

- O = Dose ordered
- W = Weight in Kilograms
- V = Volume of dose available
- C = Calibration
- A = Dose available

## Examples

Example 1. A patient remains hypotensive despite repeated fluid boluses. Epinephrine is ordered at 2 micrograms/minute (mcg/min). A 1:1,000 (1 mg/mL) vial of epinephrine is added to 250 mL of NS attached to 60 gtt/min tubing. Calculate the drops/min (gtt/min).

First, convert milligrams to micrograms.

- Dose available = 1 milligram (mg)

1 mg × 1,000 mcg

Next, use the dose formula to calculate rate.

- Dose ordered = 2
- Volume = 250 mL
- Calibration = 60
- Dose available = 1000 mcg

The answer is 30 gtt/min.

Example 2. Start Dopamine at 5 mcg/kg/min on a patient weighing 100 kilograms. Four hundred milligrams of dopamine has been mixed in 500 mL NS. Calculate the drops per minute.

First, convert milligrams to micrograms.

- Dose available = 400 mg

400 × 1,000 mcg = 400,000 mcg

Next, use the dose formula to calculate rate.

- Dose ordered = 5
- Weight = 100 kg
- Volume = 500 mL
- Calibration = 60
- Dose available = 400000 mcg

The answer is 37.5 gtt/min.

## References

- Gage, C. B., & Toney-Butler, T. J. (2017). Dose Calculation.