Two Nearly Identical Bottles: A Paracetamol Order for a 16 kg Child
A four-year-old boy weighing 16 kg is admitted to the paediatric ward with a temperature of 39.1 °C. The medical officer orders paracetamol syrup 15 mg/kg/dose every 6 hours as needed, up to four doses a day. The ward shelf holds two almost identical bottles: paracetamol 250 mg/5 mL and paracetamol 125 mg/5 mL. The intern has written 'give 10 mL of 250 mg/5 mL' on the treatment chart, and a nursing student has already told the mother the child will get 'two spoons'. The only measure at the bedside is a plastic cup graduated at 2.5 mL and 5 mL. Stock of the 250 mg/5 mL bottle is nearly finished and the pharmacist offers the 125 mg/5 mL bottle instead. The first dose was given an hour ago and the child vomited about 20 minutes after it. The ward has no paediatric oral syringes left, but the injection room has 5 mL syringes.
1. Calculate the correct dose in mg and the volume to draw from each bottle. Compare these with the intern's written order and state whether the order is safe.
Read the worked answer
Correct dose = 15 mg/kg × 16 kg = 240 mg per dose; four doses = 960 mg/day = 60 mg/kg/day, which is within the usual 75 mg/kg/day ceiling.
- From 250 mg/5 mL: 5 mL ÷ 250 mg × 240 mg = 4.8 mL per dose.
- From 125 mg/5 mL: 5 mL ÷ 125 mg × 240 mg = 9.6 mL per dose.
The intern's order of 10 mL of 250 mg/5 mL = 500 mg per dose = 31 mg/kg/dose, and 2,000 mg/day = 125 mg/kg/day. That is roughly double the correct dose and far above the safe daily limit, especially for a febrile child who may be drinking poorly. Note that 10 mL is almost exactly the right volume of the 125 mg/5 mL bottle - the error looks like a bottle mix-up, which is exactly why look-alike bottles must be stored apart. The order is unsafe: do not give it, and get it corrected in writing.
2. What will you do before administering the dose, including how you will measure 4.8 mL?
Read the worked answer
Hold the dose and act in this order:
- Clarify with the prescriber and obtain a written correction: paracetamol 240 mg = 4.8 mL of 250 mg/5 mL every 6 hours if needed.
- Confirm the weight on the same scale, ask about allergy or a previous reaction to any fever syrup, and check whether another medicine (for example a cold combination syrup) also contains paracetamol, because the doses add up.
- Measure accurately. The 2.5/5 mL cup cannot measure 4.8 mL. Draw 4.8 mL into a 5 mL syringe without a needle, label it 'oral use only', and give it into the side of the mouth. If the 125 mg/5 mL bottle must be used, recalculate to 9.6 mL and rewrite the chart; never switch bottles silently.
- Second-person check of drug, strength, dose, volume and time.
- Document the time, drug, strength, dose in mg and in mL, route and batch, and tell the mother the exact volume so she can also check.
3. The child vomited 20 minutes after the first dose. Should the dose be repeated? What would you decide if the vomit had occurred 40 minutes after the dose?
Read the worked answer
Vomiting within about 15–30 minutes means most of the dose was probably not absorbed, so repeat the full 240 mg dose once, then continue the 6-hourly schedule from that time. Vomiting after 30–45 minutes usually means absorption is largely complete, so do not repeat - give the next scheduled dose and record the vomit.
Never repeat a dose more than once, and count the repeat in the day's total; the maximum is four doses in 24 hours.
Check the vomited material for syrup, look for any spilled or hidden medicine in the bed, and note the exact time of the vomit and of any repeat dose. If vomiting continues, if the child cannot keep fluids down, or if he becomes drowsy, inform the medical officer - the rectal or intravenous route may be needed, and dehydration must be assessed before the next dose is planned.