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Table 3 Metabolic parameters of some drugs generated from Vmax and Km using modified Michaelis-Menten equations

From: Application of modified Michaelis – Menten equations for determination of enzyme inducing and inhibiting drugs

Drug Binding Site Metabolites Dose (mg) Vmax Km Cs R CMR Vo Clint % saturation S/Km Status pH References
Theophylline (mg) Adenosine receptor/RNA 1, 3 – DMU 300 34.2 14.2 1.08 0.18 14.85 2.60 2.41 7.07 0.08 Inducer Weak base [25]
1 – MU 300 13.1 9.3 1.12 0.17 5.69 1.58 1.41 10.74 0.12 Inducer Week base [24]
3 - MX 300 4.9 2.0 2.0 2.45 2.13 4.90 2.45 50.00 1.00 Inducer Weak base [25]
Mibefradil (mg) Globulin Dealkylated 100 6.79 70.2 1.02 0.003 2.95 0.10 0.097 1.43 0.01 Inhibitor Base [57]
Voriconazole (ng) Albumin/globulin Hydroxylated 400 114 1.15 7.67 661.2 49.51 160.33 99.13 86.96 6.67 Inducer Acidic [6]
Metronidazole (μm) Plasma protein 2-hydroxy 300 0.366 0.911 1.00 0.00 0.16 4.02 4.02 52.32 1.10 Inhibitor Acidic [23]
metronidazole 300 0.527 0.235 0.31 −2.10 0.23 0.14 2.24 56.88 1.32 Inhibitor Acidic [1]
Isoniazid (mg) Protein Isonicotinic acid 250 30.87 1.669 2.50 27.75 13.41 46.25 18.50 59.97 1.50 Inhibitor Base [35]
Puromicin(mg) Ribosome 5′-monophosphate 100 193.9 0.0435 0.00 0.00 84.21 0.00 0.875 0.00 0.00 Inhibitor Acidic-basic [15]
Phenytoin (mg) Na + receptor Phenylhydantoin 300 8.25 9.43 0.049 0.00 3.58 0.00 0.043 0.52 0.01 Inducer Base [7]
R – Thiopental(mg) GABAA 120 0.86 20.0 1.03 −0.002 0.37 0.04 0.042 4.90 0.05 Inducer Base [10]
Phenytoin (mg) Na + receptor Hydroxyphenytoin 300 28.0 91.0 1.01 0.23 12.16 0.31 0.308 1.10 0.01 Inducer Base [37]
S – Thiopental (mg) GABAA 300 1.01 24.0 1.04 0.002 0.44 0.04 0.042 4.15 0.04 Inducer Base [33]
Thymidine(mg) Nucleoside Baminoisobutyric acid 2.45 45.5 1.00 0.00 1.06 0.053 0.053 2.15 0.02 Inducer Acidic [11]
Thymine(mg) DNA 2.55 82.5 0.98 0.00 1.11 0.03 0.030 1.17 0.01 Inducer Base [12]
Fluorouracil(mg) Albumin Dihydrofluorouracil 2.16 39.8 1.02 0.006 0.94 0.06 0.054 2.50 0.03 Inducer Base [13]
Tylosin(mg) Ribosome Relomycin 110 0.018 0.37 0.58 −0.021 0.01 0.028 0.049 61.05 1.57 Inducer Acid-basic [1]
  1. Keys: Vmax Maximal velocity (mg/h), Km Metabolism constant (mg/L), Cs Concentration of substrate (μg; ng; μm; mg), R Rate of endogenous substrate production (h), CMR Cellular metabolic rate (/h), Vo Initial velocity (mg/h), Clint Proportionality constant between rate of metabolism and the drug substrate concentration at the enzyme site Cs, % saturation Extent of enzyme saturation; 3-MX: 3-methylxanthine; 1,3-DMU:1,3 dimethyluric acid;1-MU:1-methyluric acid