A Prescription That Does Not Add Up
A 9-year-old child (weight 28 kg) is brought to your community pharmacy with a handwritten prescription for oral amoxicillin suspension. The prescriber has written: 'Amoxicillin 250 mg/5 mL - give 7.5 mL three times daily for 10 days.' The parent says the child had a rash after amoxicillin two years ago but 'the doctor said it was fine this time'. The prescription is dated today and signed, but the prescriber's registration number is missing and the dose is written in figures only. Your stock is a 100 mL bottle of 250 mg/5 mL suspension with 7 days' shelf life after reconstitution. The pharmacy has no way to reach the prescriber until the next morning.
1. Calculate the prescribed daily dose in mg/kg/day and assess whether it is within the usual range for a child, showing your arithmetic.
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Concentration is 250 mg per 5 mL = 50 mg/mL. Each dose: 7.5 mL × 50 mg/mL = 375 mg. Daily dose: 375 mg × 3 = 1125 mg/day. Per kg: 1125 mg ÷ 28 kg = 40.2 mg/kg/day, divided into three doses of about 13.4 mg/kg. For oral amoxicillin in children, the common range is roughly 25–50 mg/kg/day (higher, up to about 80–90 mg/kg/day, for certain indications such as acute otitis media). 40 mg/kg/day is therefore within a plausible range - the arithmetic is not the problem. The problem is that a dose written only in figures, with no units spelled out and no indication, cannot be verified as intended. Best practice is to clarify with the prescriber rather than silently 'correct' anything.
2. Identify the legal and clinical red flags on this prescription and state what you would do before dispensing.
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Legal/administrative red flags: (1) missing prescriber registration number - a required element on a valid prescription in most jurisdictions; (2) dose in figures only, not figures and words, which increases the risk of a 10-fold misreading; (3) no indication stated. Clinical red flag: a documented rash after amoxicillin. A rash on amoxicillin can be a true penicillin allergy, or it can be a benign maculopapular rash associated with a viral illness (very common in children). Either way, the history must be taken seriously and the prescriber must confirm the decision with the allergy documented. Action: do not dispense yet. Contact the prescriber the next morning to (a) obtain the registration number, (b) confirm the dose and write it in words, (c) confirm the indication, and (d) document the allergy discussion and the prescriber's explicit decision. Record the intervention in the pharmacy log. If the parent cannot wait and the prescriber is unreachable, explain the reason for the delay and offer to contact the prescriber yourself - never dispense on an unverified prescription just to avoid inconvenience. If the child were acutely unwell, direct the parent to urgent care rather than guess.
3. Assuming the prescription is later confirmed unchanged, how much suspension must you supply, can one 100 mL bottle cover the course, and what labelling and counselling points apply?
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Total volume: 7.5 mL × 3 doses/day × 10 days = 225 mL. One 100 mL bottle is not enough; you need at least three bottles (300 mL). But the reconstituted suspension has only a 7-day in-use shelf life, so a single bottle cannot carry the child through 10 days. Supply two bottles: dispense and reconstitute one now (100 mL, enough for 13 doses ≈ 4.3 days), and instruct the parent to return on day 4–5 for the second bottle to be reconstituted fresh. Alternatively, dispense two bottles with clear written instructions on when to reconstitute the second. Label: patient name, drug, strength (250 mg/5 mL), dose (7.5 mL = 375 mg), frequency (three times daily), duration, route, 'shake well before each dose', 'complete the full course even if the child feels better', storage (refrigerate, do not freeze), date of reconstitution and discard date, pharmacy name and phone. Counselling: measure with the oral syringe provided, not a kitchen spoon; shake well; give with or without food as directed; watch for rash, diarrhoea, or vomiting and report them; keep out of reach of children. Confirm the allergy discussion is documented.