1. In the past, children’s medication was discounted according to weight or age. With the development of pharmacodynamics and pharmacogenetics, after many medical scientists’ research, it was found that this calculation method has certain defects. In recent years, foreign countries have recommended that drugs be calculated according to pediatric body surface area, which is suitable for both children and adults, and is scientifically stronger. Therefore, in recent years, the body surface area calculation method has been advocated to determine the dose of medication for children, which is calculated as follows.
(1) Body surface area and dose calculation for children weighing ≤30kg.
Pediatric body surface area (m2) = body weight (kg) × 0.035 + 0.1
Pediatric dose = (adult dose × pediatric body surface area)/1.7 (where: 1.7 is the average adult body surface area in China)
(2) Body surface area and dose calculation for children weighing >30kg.
Body surface area of children (m2) = 1.05 + (weight – 30) × 0.02
(Empirically, for every 5kg increase in body weight, the body surface area increases by 0.1m2, for weight > 50kg, the body surface area increases by 0.1m2 for every 10kg increase in body weight)
35kg, body surface area = 1.15m2 (empirically 1.10+0.10=1.20m2)
40kg, surface area = 1.25m2 (empirically 1.10+0.20=1.30m2)
45kg, body surface area = 1.35m2 (empirically 1.10+0.30=1.40m2)
50kg, body surface area = 1.45m2 (empirically 1.10+0.40=1.50m2)
55kg, body surface area = 1.55m2 (empirically 1.50+0.05=1.55m2)
60kg, body surface area = 1.60m2 (fixed value)
65kg, body surface area = 1.65m2 (empirically 1.60+0.5=1.65m2)
70kg, body surface area = 1.70m2 (fixed value)
2. British National Formulary: For a child weighing ≤30kg, the dose may be (weight x 2)% times that of an adult;
For a child >30kg, the dose may be (weight +30)% times that of an adult.
3. The current measurement of body surface area in children follows the widely used multidimensional Du Bois formula.
Body surface area S(m2)=H0.725×W0.425×71.84, where H is height (cm) and W is weight (kg).
4. General adults and children apply the Hsu Vincent’s (Stevenson) formula.
Body surface area S(m2) = 0.0061 × height (cm) + 0.0128 × weight (kg) – 0.1529