The following is an overview of the type of questions you might expect to encounter in an MMI Calculation station, along with how to approach them.
An eight year old child is on your ward. He needs an intramuscular injection of 0.3mg adrenaline solution. Adrenaline is available as an injection of 500 micrograms/ml. How many millilitres of injection are therefore needed to supply the required dose?
Answer: 0.6mls
Explanation: 0.3mg is 300 micrograms. If there are 500 mcg in 1 ml of injected solution, then we need 0.6mls to get 300 mcg, as 0.6 * 500 = 300.
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A patient requires an intravenous infusion of phenytoin at a rate of 275mcg/kg/minute. The solution to be used is a 1% injection solution. The patient weighs 62kg. Therefore how much of the drug would be administered after an hour? Provide your answer in grams.
 Answer: 1.023g
Explanation: 275 mcg per 1kg per minute = 17050 mcg when multiplied by 62. Then multiply further by 60 to get the rate in an hour, which gives 1,023,000 mcg = 1023mg = 1.023g.
A drug has an elimination half-life of 14 hours. If we are to assume that it is completely absorbed and 1200mg of the drug is administered as the dose, how many mg would you expect to remain in the body after 48 hours? Assume the drug in question has first order pharmacokinetics. Give your answer to 2 decimal places.Â
Answer: 117.86mg
 Explanation: Start with 1200mg, so after 14 hours we have 600, then after another 14 hours we have 300mg, after another 14 hours halved again to 150mg – but this equals to 42 hours and we need to work out for 48 hours. We must therefore consider that in the next halving between 150mg to 75mg in 14 hours the drug is reduced by 75mg. Thus in one hour the drug reduces by an average of 5.36mg and you can then multiply this value by 6 to work out total drug depletion in 6 hours = 32.14mg. Subtract 32.14 from 75 to get 42.86mg being depleted in 8 hours. Add 42.86 to 75 to get 117.86 remaining after the 48 hour time period.
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A patient has been admitted onto the ward. They are to receive 1 litre of glucose 7.5% solution over a period of 8 hours. What would be the rate of delivery of this solution? Provide your answer in ml/min and round the answer to the one decimal place.
Answer: 2.1mls per minute
Explanation: 1L is 1000 mls. Therefore in 8 hours, which is 480 minutes, we would have 1000mls. Thus we need to divide 1000 by 480, which gives us a value of 2.08. Rounded to one decimal place this is 2.1 mls per minute.
