Body surface area, dose calculation

If the drug dose is based on body surface area (m2) the same meHiod of calculation may be used. 

The dose of drags for children as well as adults may be adjusted based on the body surface area. The normal adult body surface area is 1.73 m2. The body surface area may be calculated in many ways. The following equation provides a useful estimate of the surface area when the height (in cm) and weight (in kg) of the patient are known ... 

The dose modifications based on body surface area provide a better approximation of dose than the dose based on body weight. The general equation to calculate the child s dose by the surface area method is as follows ... 

Convert the NOAEL to the human equivalent dose (HED) using the data from Table 5.3 (calculations are based on body surface areas). 

When correction for differences in body size is based on body surface area, the power n in the allometric equation is 2/3, or 0.67, and the human dose Xhuman (expressed in mg) can be calculated as follows ... 

Body surface area calculation square root (height in cm x body weight in kg divided by 3600). High doses required in infants < 1 yr because of kinetic variability. 

For children who can swallow capsules and for whom the current capsule formulations allow appropriate weight or body surface area calculated dosing, additional options to replace LPV/r include SQV/r and IDV/r. 

Dose can be calculated more accurately by body surface area (BSA). 

There are many circumstances in which a fixed drug dose is likely to be ineffective or toxic in a significant number of individuals, e.g. cytotoxic chemotherapy, aminoglycoside antibiotics. It is usual then to calculate the dose according to body weight. Adjustment according to body surface area is also used and may be more appropriate, for this... 

Children require and tolerate a larger mg/kg dose than adults and cannot be considered as small adults. For example, the doses of digoxin required to maintain mean plasma concentrations of about 1-1.5 ng/ml are 15-20 pg/kg per day for children 4 weeks to 2 years of age, 10-15 pg/kg per day for children 2-12 years of age, and 4-5pg/kg per day for adults. Reasonable estimates of the doses required in children are often obtained by calculating the child s dose on the basis of body surface relative to that of an adult. An estimate of body surface area may be made from Eq. (11). 

Calvert formula for dose modifications Dose (mg) = target AUC x (CLcr -E 25) CIcr calculated using Cockcroft-Gault equation note that the calculated dose is total dose, not dose per m body surface area Bone marrow recovery may require 6-8 weeks postadministration not a vesicant vein irritation and facial flushing may be related to alcohol vehicle... 

Prescribing, dispensing and administration of medicines for children pose a unique set of risks, predominantly because of the wide variation in body mass, which requires doses to be calculated individually based on patient age, weight or body surface area, and their clinical condition. This increases the likelihood of errors, and tenfold errors, as... 

Gurney, H. P., Ackland, S., Gebski, V. and Farrell, G., Factors affecting epimbicin pharmacokinetics and toxicity evidence against using body-surface area for dose calculation, /. Clin. Oncol, 16, 2299, 1998. 

The similarities in VX sensitivity between sheep and humans may, in part, be accounted for by similarities in rates of metabolic detoxification of the agent. The latter can be estimated from a comparison of body surface areas (based on body weight) as is done for animal-to-human extrapolations used in EPA cancer risk assessments (USEPA 1996c). Using this approach, the human equivalent dose for the 0.06 ig/kg/d sheep LOAEL in the Rice et al. study can be calculated as ... 

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