Nevertheless, some dosing guidelines for various age groups are available, but the physician must monitor blood levels to adjust doses to attain the desired levels. Drugs must be dosed by weight. While this is well known by pediatricians, physicians caring for adults often overlook the fact that the range of weight encountered in the adult patient may be greater than that seen in a pediatric clinic. Adults can weigh from 45 to 200 kg. In addition, other prescription medications, smoking, alcohol, and diet may significantly affect drug metabolism.
Racial background has a major effect as well.
Unfortunately, this area has not been thoroughly studied. Carbamazepine dosing is complicated because it is autoinduced and is also induced by other drugs. If the person is receiving an inducer such as phenytoin, doses may need to be doubled. There are very few studies in the elderly, but preliminary data indicate that metabolism in the elderly is only half of that in younger adults. It is not known if the elderly have autoinduction of carbamazapine metabolism.