Adjusting therapeutic dosage regimens to optimise the balance of benefit to harm
Dosage regimens should generally be individualised, depending on features of the patient that can alter the drug's pharmacokinetics (disposition in the body) or pharmacodynamics (therapeutic and adverse effects). It is usually good practice to start with a low dose, gradually increasing it according to response; a loading dose can produce a response more quickly if necessary. The most important factors that alter drug pharmacokinetics are renal insufficiency and liver disease. The most important factors that alter drug pharmacodynamics are fluid and electrolyte abnormalities, age and liver disease. Careful monitoring can help to avoid adverse drug reactions and interactions during long-term therapy, particularly if the disease changes with time. The more even the balance of benefit to harm, the more care needs to be taken in monitoring therapy.