Chapter 17 - Page 2

Linear Plot of Morphine Concentration versus Time after Codeine Administration

Try simulating morphine concentration versus time after oral codeine administration. Select individuals with low, intermediate or high CYP2D6 activity. Add additional lines with different parameter values using the Add Line button.

Figure 17.2.1 A Simplified Pharmacokinetic Model for Codeine Transformation into Morphine

The model in Figure 17.2.1 is a simplification of codeine and morphine pharmacokinetics. Codeine is metabolized to a variety of compounds including morphine. Also, both codeine and morphine are probably better described using a two compartment model.

The lines in the plot above were calculated using Equation 17.2.1, derived from the model, Figure 17.2.1, for codeine metabolism using Laplace transforms.

Equation 17.2.1 Concentration of Morphine after Oral Administration of Codeine

Table 17.2.1 Some Parameters Describing Codeine Metabolism

Parameter Value Units
Dose 30 mg
F 0.51
ka 2.282 hr-1
kel (codeine) 0.211 hr-1
V (codeine) 3.45 x 70 = 2421 L
V (morphine) 701 L
kel (morphine) 0.31 hr-1
km (high) 0.0135 hr-1
km (intermediate) 0.00659 hr-1
km (low) 0.000610 hr-1
References and Notes

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