A patient with HIV infection is receiving 200 mg of didanosine PO bid. The pharmacy only has powder packets with 167 mg each, to be mixed with 4 oz of water. How many packets should the patient mix? How much should the patient take? How can it be measured?
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Solution
\(200\, mg\times \frac{4\, oz}{167\, mg}= 4.8\, oz\)
*The patient will have to mix two packets, each in 4 oz of water, and drink 4.8 oz measured in a calibrated measuring cup. If a cup that measures milliliters is available, then:
\(4.8\, oz\times \frac{30\, mL}{1\, oz}= 144\, mL\)
OR
\(144\, mL\times \frac{1\, tbsp}{15\, mL}= 9.6\, tbsp\)
You need to administer furosemide (Lasix) 2 mg/minute via continuous IV infusion on a controller. Pharmacy has sent a bag of Lasix 400 mg diluted in D5W 250 mL. How many milliliters per hour will you set on the controller?
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Solution
\(\frac{2\, mg}{minute}\times \frac{250\, mL}{400\, mg}\times \frac{60\, minutes}{1\, hour}= 75\, mL/hour\)
You need to administer 400 mg of erythromycin PO. You have on hand a suspension of 125 mg/5 mL. How much will you prepare?
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Solution
\(400\, mg\times \frac{5\, mL}{125\, mg}= 16\, mL\)
You need to administer 250 mg of erythromycin PO. You have on hand 0.5 g tablets. How many tablets will you give?
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Solution
\(250\, mg\times \frac{1\, g}{1,000\, mg}\times \frac{1\, tablet}{0.5\, g}= 1/2\, tablet\)
The physician orders alprazolam (Xanax) 0.5 mg PO. You have on hand Xanax 0.25 mg tablets. How many will you give?
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Solution
\(0.5\, mg\times \frac{1\, tablet}{0.25\, units}= 2\, tablets\)
You have on hand penicillin 300,000 units/mL. Your order reads penicillin 1,000,000 units IM. How will you fill the syringe?
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Solution
\(1,000,000\, units\times \frac{1\, mL}{300,000\, units}= 3.3\, mL\)
Your patient needs 2,000 mL of D5W IV over 24 hours, to be delivered with a tubing set with a drop factor of 15. How many drops per minute will you set for an infusion rate?
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Solution
\(\frac{2,000\, mL}{24\, hours}\times \frac{1\, hour}{60\, minutes}\times \frac{15\, gtts}{mL}= 21\, gtts/minute\)
Your patient needs 2,000 mL of saline IV over 4 hours for severely deficient fluid volume. How many milliliters per hour will you set on a controller?
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Solution
\(\frac{2,000\, mL}{4\, hours}= 500\, mL/hour\)
You are caring for your ill grandmother at home. She has an order for magnesium hydroxide/aluminum hydroxide (Maalox) 10 mL PO prn stomach upset. How do you instruct her to measure her dose using household measuring spoons?
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Solution
\(10\, mL\times \frac{1\, tsp}{5\, mL}= 2\, teaspoons\)
Your patient is taking acetaminophen (Tylenol) gr 15 every 6 hours PO for headache pain. You know the maximum safe dose is 4 g in 24 hours. Is the dose safe?
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Solution
\(\frac{15\, gr}{dose}\times \frac{4\, doses}{day}\times \frac{1\, g}{15\, gr}= 4\, g/day\)
*The dose is at the upper limit of a safe dose.