Drug Calculation Samples

 

Conversion Table

1 pound (lb)

0.454 kg

 

1 kg

2.2 pounds (lb)

 

1 quart

32 oz

960 ml

1 pint

16 oz

480 ml

1 glass

8 oz

240 ml

1 teacup

4 oz

120 ml

1 tablespoon

0.5 oz

15 ml

1 teaspoon

 

5 ml

15 drops

 

1 ml

1 ounce

30 ml

 

1 ml

1 mg

 

 

SID = once a day

BID = twice a day

TID = three times a day

QID = four times a day

 

 

1.      Amoxicillin is dosed at 5 mg/lb TID. Your patient is a two year old weighing 32 pounds.

  1. How much amoxicillin will they need per dose?
  2. How much amoxicillin will they need per day?
  3. If amoxicillin comes as a liquid with 50 mg/ml, how many ml (round up to the next ¼ ml) will the patient need per dose?

2. Azithromycin is used to treat respiratory infections. The dose is 500 mg QID on day 1, then 250 mg per day for 4 days. Your patient is a 185 pound man.

  1. How much Azithromycin will he need on day 1?
  2. How much Azithromycin will he need for 5 days of treatment?
  3. If Azithromycin comes as 200 mg/5 ml, how many ml of the solution will he need for the entire treatment?

3. Fascarnet is dosed at 60 mg/kg TID. Your patient is a 152 pound woman.

  1. How much Fascarnet does she need per dose?
  2. How much Fascarnet does she need per day?
  3. If she needs 3 days of medication how much Fascarnet in g will she need?

4. Ganciclovir is dosed at 5 mg/kg BID for 3 weeks. Your patient is 178 pound man.

  1. How much Ganciclovir will he need per dose?
  2. How much Ganciclovir will he need per day?
  3. How much Ganciclovir will he need for the entire treatment?
  4. If the drug costs $60/day how much will it cost him for the entire treatment?

5. Trimethoprim sulfamethoxazole is dosed at 10 mg/kg per day in 2 equal doses. A 136 pound female patient with a urinary tract infection is prescribed this drug.

  1. How much Trimethoprim sulfamethoxazole will this patient need per day?
  2. How much Trimethoprim sulfamethoxazole will this patient need per dose?
  3. If the drug comes as 960 mg tablets and 480 mg tablets, which one would you prescribe? Keep in mind the patient has a pill “phobia” so the fewer number of pills she has to take the better it will be for her. (You can give up to 240 mg extra per dose safely.)
  4. If cost, on the other hand, is an issue, the 960 mg tablets cost $0.36 each and the 480 mg tablets cost $0.29 each, which size tablets would be the best choice for this patient. Keep in mind that both tablets can be broken in half but not in quarters.