The Math: From Pen Price to Monthly Cost
The calculation is simpler than it looks. Divide the pen price by the doses per pen to get the cost per dose. Then multiply that figure by the number of doses you'll use in a month.
In letters, it works like this. If a pen costs X reais and holds Y doses, as the bula lists, the cost per dose is X divided by Y. If your schedule calls for Z doses in a month, the monthly medication cost is that per-dose figure times Z.
Now a worked example with invented numbers. Imagine a fictional pen priced at R$ 500 that holds 4 doses. Its cost per dose would be R$ 125, and four doses in a month would come to R$ 500. These values exist only to show the arithmetic. They are not market prices, so replace them with figures from your own label and quotes.
Price per milligram follows the same logic. Divide the pen price by the total milligrams the bula lists for that pen. Using the same invented pen, if it held 2 mg in total, the price per milligram would be R$ 250. A lower figure means less money for each unit of medication, which helps when two presentations sit side by side. Take the total milligrams from the bula, not from the box.
A flat monthly number can still mislead you. Treatment plans often include a titration phase, where the dose rises in steps before reaching a maintenance level. The number of pens you need can change from month to month during that phase. The bula describes the dosing interval and any dose steps for each product, so read them there rather than working from memory.
