Monthly consumption may be collated with data obtained from:

• Bin (stock) cards,
• Daily use record, daily cash record,
• Drug register.

Normally, monthly consumption is obtained by:

• Calculating the average consumption over a period of time (e.g. six months)
• Or dividing the total consumption over the period by the number of months the drug dosage form was consumed.

Example 1: Monthly consumption

The first method of calculating monthly consumption is to add the quantity of drugs in stock at the beginning of a period (e.g., six months) to the quantity of drugs received during that same period and then subtract the quantity of drugs remaining at the end of the period.

April 2000, quantity of paracetamol 1,000 × 500-mg tablet containers in stock = 14
June 2000, quantity of paracetamol 1,000 × 500-mg tablet containers received = 8
September 2000, quantity of paracetamol 1,000 × 500-mg tablet containers, remaining stock = 6
Therefore, total quantity of paracetamol 1,000 × 500-mg tablet containers consumed over a six-month period = 14 + 8 - 6 = 16.

Average monthly consumption = 16/6

Average monthly consumption to the nearest container = 2 2/3

Example 2: Monthly consumption

A second method of calculating the average monthly consumption is to obtain data on consumption from the bin card on a monthly basis and then find an average over a period of time.

Average monthly consumption is

Average monthly consumption of container to the nearest container = 3

Example 3: Monthly consumption

A third method of calculating average monthly consumption is to obtain data on actual consumption from the daily use record or daily use/cash record.

Data of monthly consumption of paracetamol 500-mg tablets over a six-month period.

Each container has 1,000 tablets. Therefore the average monthly consumption of 1,000-tablet tin = 2633.3/1000 = 2.6 tins

Average monthly consumption of paracetamol 500-mg tablets to the nearest container = 3