QUESTION 1
For treating epilepsy of all forms, except typical absences, the recommended oral dose for children under 11 years old is initially 1-1.5mg/kg twice daily (Joint Formularies Committee, 2019). The licensed product available in the UK is a 15mg/5mL oral solution. What range of volumes could be administered to a 5kg child to provide doses in the appropriate starting range?
- 1mg/kg × 5kg = 5mg per dose
- 15mg/5ml = 3mg/ml
- 5mg per dose / 3mg/ml = 1.7ml (to one decimal place)
- 1.5mg/kg × 5kg = 7.5mg per dose
- 15mg/5ml = 3mg/ml
- 7mg per dose / 3mg/ml = 2.5ml (to one decimal place)
- Therefore doses between 1.7 to 2.5 ml would be an appropriate oral initiation dose for a 5kg child.
QUESTION 2
What volume should be specified on a prescription for our 5kg patient for the first 28 days of treatment if they are started on 1.5mg/kg per dose.
- 2.5ml per dose × 2 doses per day = 5ml day
- 5ml per day × 28 days = 140ml (one hundred and forty millilitres) for the course.
QUESTION 3
Given that Phenobarbital Elixir BP contains ethanol 38%v/v (eMC 2016) how much ethanol will our 5kg patient be consuming each day from the higher starting dose of phenobarbital calculated in 1) above?
- 38%v/v = 38ml of ethanol per 100ml = 0.38ml per ml
- Initial dose will be 2.5ml per dose, since this is given twice per day the daily amount will be 5ml
- 5ml × 0.38 ml of ethanol per ml = 1.9 ml of pure ethanol.
QUESTION 4
Assuming our patient is commenced on the higher starting dose, scale up their alcohol exposure to estimate an equivalent weekly dose in terms of glasses of wine for a 70kg adult. A standard glass of 12% wine is around 2 units of alcohol.
- 1.9ml ethanol per day × 7 days = 13.3 ml per week
- 13.3ml per week / 5kg = 2.66 ml/kg/week
- 6.72ml/kg/week × 70kg = 186.2 ml/week
- 186.2ml/week divided by 10ml/unit = 18.6 units per week
- 18.6 units divided by 2 units per glass of wine = 9.3 glasses of wine per week
- For comparison adults are advised to drink less than 14 units per week (7 glasses of wine).