Question

A 4-year-old F (33 pounds) with a parasitic infection needs to receive metronidazole 30 mg/kg/day in 3 divided doses orally for 14 days. She cannot swallow pills. You find the following formula for metronidazole oral suspension. METRONIDAZOLE ORAL SUSPENSION FORMULA Metronidazole 250 mg tablets 12 Ora-Plus:Ora-Sweet 1:1 QSAD 150 ml 1. How many milliliters of the metronidazole oral suspension would the patient need to take for each dose? How many teaspoonfuls would this be? How many tablets of metronidazole 250 mg would you need to use to compound enough metronidazole oral suspension for the entire course of treatment the patient needs to receive? III. What is the percentage strength concentration of the metronidazole oral suspension that you have compounded to fill this prescription?

Answer 1

Weight of patient is 33 pounds.

2.2 pound = 1 kgs approximately

33 pounds = (33/2.2) which is 15 kgs

Drug required per day = 30 mg/kg/day

For 15 kg baby it is 30*15 = 450 mg per day.

This 450 mg should be given in 3 divided doses for 14 days, which means 150mg per dose.

The given suspension contains 150ml solvent

solute is 12 tablets each of 250mg = 3 grams of solute.

I

Amount of drug required in each dose = 150 mg

150 ml of oral suspension contains 3 grams ( or 3000mg) of metronidazole

Amount of drug present in 1ml suspension = (weight of drug / volume of suspension)

which is 3000/150 mg/ml = 20 mg/ml

Volume of solution containing 150mg metronidazole =

(required drug dose / weight of drug present in 1ml of suspension)

which is 150/20 = 7.5 ml

one teaspoon is 5ml approximately

7.5ml corresponds to 1.5 teaspoons

For each dose the patient needs to take 7.5 ml oral suspension which corresponds to 1.5 teaspoons.

II

Daily requirement of metronidazole is 450mg. It is required for 14 days.

Total requirement of metronidazole for 14 days = Daily requirement * number of days

which is 450 * 14 = 6300 mg.

each tablet contains 250mg metronidazole.

For 6300 mg, the required number of tablets = (total dosage of drug required / drug in one tablet)

which is 6300 / 250 = 25.2 tablets

25.2 tablets of 250mg metronidazole tablets are needed for entire course.

III

The volume of oral suspension is 150 ml and it contains 3 grams of metronidazole.

The w/v percentage strength concentration of the suspension =

( weight of drug in grams * 100 / volume of suspension)

which is ( 3 * 100 / 150 ) = 2% w/v

The w/v percentage strength concentration of the suspension is 2 %.

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