The doctor orders 0.4 mg of a drug b.i.d. If each pill contains 0.4 mg and there are 30 pills in the bottle, how many days will the bottle last?

To determine how many days the bottle will last, first recognize that the medication is prescribed at a dosage of 0.4 mg twice a day, referred to as b.i.d. (bis in die, or twice a day). Since each pill contains exactly 0.4 mg, a patient will consume one pill for each dose.

Calculating the daily pill consumption:

• Daily, one pill will be taken in the morning and one in the evening, resulting in a total of 2 pills per day.

Next, consider the total number of pills available:

• The bottle contains 30 pills.

To find out how many days the medication will last, divide the total number of pills by the daily consumption:

• Since the patient consumes 2 pills per day, divide 30 by 2, which equals 15 days.

Thus, the bottle will last for 15 days. This understanding highlights the importance of calculating total dosages correctly based on frequency (b.i.d.) and the amount contained within each unit of medication.