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An overview of prescribing drug dose in paediatric inpatient department, easily explained how to calculate infusion rate
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Techniques of calculation and prescribing drug dosage in
pediatric practice
Dr. Paul, Shubhra PrakashAssistant Registrar
Rajshahi Shishu(children) Hospital
Dose of Commonly used drugs (parenteral)
Drugs Indication with Dose
Frequency Preparation
Aminophylline 5mg/kg/dose stat2.5mg/kg/dose for maintenance therapy
125mg/5mL
Meropenem Other than meningitis 20-30 mg/kg/dose
8 hourly 500 mg/vial
Meningitis60mg/kg/dose
8 hourly
Azithromycin 10mg/kg/dose Once daily for 3 days
500mg/vial
Vancomycin 10-15mg/kg/dose 8 hourly 500mg/vial
Dopamine 5gm/kg/min followed by gradual increase up to 20gm/kg/min
200mg/5mL vial
Dose of Commonly used drugs (parenteral)
Drugs Indication with Dose
Frequency
Preparation
Netilmycin 3mg/kg/dose 12 hourly 50mg/2mL
Phenobarbitone 20mg/kg/dose as loading dose
8 hourly 200 mg/ml
Maintenance5-20mg/kg/day in divided dose
Clarithromycin 15mg/kg/day in2 divided dose
12 hourly 500mg/vial
Phenytoin 20mg/kg/dose as loading dose
125 mg/5ml
Maintenance5-20mg/kg/day in divided dose
Relation of Dosage frequency with weight and age
Once daily
Twice daily
Thrice daily
Neonate
Children
Adult
Dosage frequency of Gentamycin for an example
The lesser is the weight the more is the dilution
The younger the child the more is the dilution
Weig
ht
Age
Example
Example I with Meropenem
Example II with Azithromycin
Example I
Case I:
• A 4 months old child weighing 5kg requiring Meropenem for an indication of meningitis.
How will you calculate the dose and infusion rate?
Basic Calculation
As the indication is meningitis the baby will
receive Injection Meropenem 60mg/kg/dose
8 hourly.So the dose for this baby is
300mg/kg/dose
Example I with meropenemAs Meropenem is to be infused not less than 30 minutes, it should be infused with IV fluid. So for the example case IV fluid of choice either Normal saline or Dextrose in aqua or Dexstrose saline is chosen. A measured volume , suppose 30 ml may be taken as carrier for meropenem infusion
Example I with meropenem
A vial of Meropenem contains 500mg of active drug in powder format. So it should be reconstituted with distilled water. Here comes the measurement of Dilution. If smaller dose is required the dilution should be with more amount of diluents and vice versa.
Example I with meropenemSo if dilution is made with 10 ml of D/W then each ml will contain 50 mg of the drug, similarly if dilution is made with 5 ml of D/W then each ml will 100 mg of meropenem. From this diluted drug the exact dose is taken and poured into measured infusion fluid and to be infused.
Example I with meropenem
In our example case I the dose is required 6 ml (if diluted with 10 ml D/W ) or 3 ml (if diluted with 5 ml D/W). Now this 3 or 6 ml is poured in to desired amount of fluid to be infused cat calculated time.
Calculation of infusion rate
e.g. 30 ml fluid should be infused over 1 hour.
So infusion rate is 30ml/hr which stands for 30ml/60min i.e. 0.5ml/min is the infusion rate.
Then 0.5ml/min means
0.5 X 15 drops/min
=7.5 drops/min (if used with infusion set)
=7.5X 4 drops/min (if used with micro burette )
= 30 drops/min
Calculation of infusion rate
e.g. 30 ml fluid should be infused over 1/2 hour.
So infusion rate is 30ml/30min which stands for 30ml/60min i.e. 1ml/min is the infusion rate.
Then 1ml/min means
1X 15 drops/min
=15 drops/min (if used with infusion set)
=15X 4 drops/min (if used with micro burette )
= 60 drops/min
Calculation of infusion rate
2 hours
• 15
1hour
• 30
So in case of infusing 30 ml fluid the rate will be as follows
(drops/min)
Example II
Case II:
• A 7 months old child weighing 8 kg requiring Azithromycin for an indication of Acute watery Diarrhea
How will you calculate the dose and infusion rate?
Basic Calculation
As the indication is acute watery Diarrhoeathe baby
will receive Injection Azithromycin @ 10mg/kg/day.
So the dose for this baby is 80mg/kg/dose
Example II with Azithromycin As Azithromycin is to be infused over 30 minutes, it should be infused with IV fluid. So for the example case IV fluid of choice either Normal saline (as it is provided with the drug as combipack) or Dextrose in aqua or Dexstrose saline is chosen. A measured volume , suppose 30 ml may be taken as carrier for Azithromycin infusion.
Example II with Azithromycin
A vial of Azithromycin contains 500mg of active drug in powder format. So it should be reconstituted with distilled water. Here comes the measurement of Dilution. If smaller dose is required the dilution should be with more amount of diluents and vice versa.
Example II with Azithromycin So if dilution is made with 10 ml of D/W then each ml will contain 50 mg of the drug, similarly if dilution is made with 5 ml of D/W then each ml will 100 mg of Azithromycin From this diluted drug the exact dose is taken and poured into measured infusion fluid and to be infused.
Example II with Azithromycin
In our example case II the dose is required 1.6 ml (if diluted with 10 ml D/W ) or 0.8 ml (if diluted with 5 ml D/W). Now this 0.8 or 1.6 ml is poured in to desired amount of fluid to be infused cat calculated time.
Example III
Case II:
• A 2 months old child weighing 4 kg requiring Netilmycin for an indication of sepsis.
How will you calculate the dose?
Example III
Recommended dose of netilmycin in sepsis is 3mg/kg/dose 12 hourly.•The baby requires 4.5mg/dose of Netilmycin only.
A vial of Netilmycin contains 50mg/2ml.
•So the baby requires only 0.18 ml of netilmycin
Example III
Here an insulin syringe of 100 U will be helpful for the required dose.
As in 100 unit insulin syringe 1ml=100 unit, 0.18 ml refers to 18 unit.
So, the dose becomes 18 unit/dose.
Thank you all