Question

A physician prescribes administration of 100 mg of a drug. The drug label states that there are 150 mg per milliliter in a multi dose vial that contains 5 ml. What is the available amount of the drug, according to the standard formula?

Answer 1

Clearly there are `7xx100*mg` doses in the phial.

Explanation:

The volume of the phial is `5*mL`.

And thus there are `5*cancel(mL)xx150*mg*cancel(mL^-1)=750*mg` of the drug in the phial.

You might suspect that the drug company is trying to make money off the consumer in that they make the consumer (i.e. the health system) buy an extra `50*mg` of the drug. You would not be wholly right.

Now of course drug companies are in the business to make money, however, by providing this extra volume, they allow the end user, the nurse, the doctor, the patient, a bit of leeway when the drug is administered. You have probably seen a nurse or a doctor, when they charge a syringe with a drug, invert the syringe, and squirt a little bit of the drug out of the end of the needle. This flushes the dead volume of the syringe and needle, and allows the volume displaced by the syringe to be an accurate reading of the the dose administered. This extra volume, so I presume, is included to allow the medical practitioner to do just that.