Eight Tablets, 100 mL, and the Wrong Expiration Date
Monday morning. A prescriber orders spironolactone 2 mg/mL oral suspension, 100 mL, for a 4-year-old (16 kg): 1.5 mL by mouth twice daily. Your pharmacy stocks spironolactone 25 mg tablets and a commercial preserved oral suspending vehicle whose manufacturer documents stability of spironolactone in that vehicle for 90 days at controlled room temperature. A technician has already crushed 8 tablets, transferred the powder, q.s.'d to 100 mL with the vehicle, and labeled the bottle "expires in 14 days, refrigerate" because that is the default. The parent later mentions she has been giving 1.5 mL three times a day from the previous bottle because it seemed to wear off. The prescriber's office confirms the order is correct as written.
1. Check the calculation and the technique. Is 8 tablets correct, and what would you fix before it goes out?
Read the worked answer
The calculation
- Final concentration wanted: 2 mg/mL x 100 mL = 200 mg of spironolactone.
- 200 mg / 25 mg per tablet = 8 tablets. Correct.
Technique points to verify, not assume
- Complete transfer. Crushing and scraping leaves residue in the mortar and on the pestle. The technician should have used geometric dilution and washed the mortar with a small portion of vehicle, incorporating it into the final volume. Verify the mortar looks clean before it goes to the sink.
- q.s. versus add. "q.s. to 100 mL" means bring the final volume to 100 mL, not add 100 mL of vehicle on top of the powder. Confirm the graduated cylinder reading was taken at the meniscus with the final volume marker reached.
- Uniformity. Tablets contain excipients that do not fully dissolve. That is expected in a suspension, but it means the bottle must be shaken vigorously before every dose, and the label must say so in plain words.
- Measuring device. 1.5 mL is not a kitchen-spoon measurement. Dispense an oral syringe with 0.1 mL graduations (3 mL or 5 mL barrel). Ask whether the family has a syringe at home and whether they are still using the old one.
- Labeling. Drug, concentration in mg/mL, dose in mL, "shake well," storage condition, beyond-use date, and a warning not to use a household spoon.
The check that catches real errors Read the finished label against the prescription out loud before it leaves the counter: 2 mg/mL, 1.5 mL twice daily. Concentration errors in pediatric suspensions are among the most common and most harmful compounding mistakes.
2. The technician's beyond-use date is wrong. What should it be, and what belongs on the label and in the compounding record?
Read the worked answer
The BUD The technician applied the water-containing oral default from USP <795> - 14 days refrigerated - which exists for situations where there is no stability information. That default does not apply here, because the manufacturer documents 90 days at controlled room temperature for spironolactone in this specific vehicle.
- Assign 90 days at controlled room temperature, based on that documented study.
- You may assign a shorter BUD if there is a practical reason (for example, the bottle will be used up in two weeks anyway), but you may not invent a longer one.
- Two things to check before writing the date: the study is for this drug in this vehicle at this concentration range, and the vehicle lot has not expired.
- Refrigeration is not automatically safer. Do not refrigerate a product documented as stable at room temperature unless the study supports it - some suspensions settle or thicken when cold.
Label contents Patient name, drug and concentration in mg/mL, dose in mL with route and frequency, "shake well before each dose," storage temperature, beyond-use date, prescription number, pharmacy contact, and the auxiliary warning against household spoons.
Compounding record Formula and sources, each ingredient with lot number and expiry, the quantity of tablets used, final volume and container, the BUD and the specific documentation supporting it, the date prepared, and the signatures of both the compounder and the pharmacist who verified it. The BUD justification is the entry an inspector will look for, and "default" is not a justification when a study exists.
3. The parent has been dosing three times a day. What are your concerns, who do you notify, and what do you tell her?
Read the worked answer
Quantify it first
- Prescribed: 1.5 mL twice daily = 3 mL/day x 2 mg/mL = 6 mg/day, or 0.375 mg/kg/day.
- Actual: 1.5 mL three times daily = 4.5 mL/day = 9 mg/day, or about 0.56 mg/kg/day - a 50% excess.
How serious is it Put it in context rather than alarming her: 0.56 mg/kg/day is still inside the usual pediatric range for spironolactone, so this is unlikely to have caused harm. But spironolactone is a potassium-sparing diuretic, and in a 16 kg child an extra 50% matters for potassium, hydration, and blood pressure. Ask directly about drowsiness, poor feeding, unusual thirst, dizziness on standing, and decreased urination.
Who to notify
- The prescriber, the same day. Report the actual daily dose and duration, ask whether potassium and renal function should be checked, and ask for a corrected written instruction.
- The pharmacist-in-charge, and complete an internal medication-use/error report if the previous label or counseling contributed. Do not skip the report because the child seems fine.
What to tell the parent
- Give the correct dose in a way she can act on: "1.5 mL, twice a day, morning and evening - not three times."
- Show her the markings on the syringe and have her draw the dose once in front of you.
- Ask why she went to three times a day. A vague or missed instruction on the old label is a systems problem worth fixing, not a lecture opportunity.
- Have her bring the old bottle in for disposal so two bottles with different instructions are not sitting in the same cabinet.
The teach-back is the part that matters. A spoken correction that does not change the syringe in her hand has not fixed anything.