Calculation of loading and maintenance doses

It may take a long time and the administration of many doses (over seven or eight) before the desired average steady-state drug concentration is attained. Therefore, an intravenous bolus loading dose (DJ may be administered to obtain an instant steady-state condition. The calculated loading dose should be such that that, at time t after its administration, the plasma concentration of drug is the desired minimum plasma concentration at steady state, that is  

Equations 11.41 and 11.42 provide the ratio of loading dose to maintenance dose required to attain the steady-state condition instantaneously when there are N elimination half lives in a dosing interval (t). Furthermore, Eq. 11.42 indicates that the more frequent the dosing (i.e. smaller N value or t), the larger is the loading dose required compared with the maintenance dose (i.e. the greater is the ratio of DJDm) in order to attain the instantaneous steady-state condition. 

From Table 11.4, it is clear that if we wish to attain immediately the desired steady-state concentration for a drug dosed at an interval equal to half the elimination half life of the drug, the loading dose required will be 3.41 times the maintenance dose of the drug. If the dosing interval is equal to the half life of the drug, the loading dose will be twice the maintenance dose. 

8 Maximum and minimum drug cancentratian at steady state 

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