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Table 4 Calculated comparative Michaelis – Menten parameters of some enzyme inducing and inhibiting drugs

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

Drug

Vmax

Km

Cs

R

CMR

Vo

CLimt

% Saturation

% Unsaturation

S/Km

Theophylline*

17.4 ± 8.7

8.5 ± 3.5

1.4 ± 0.3

0.9 ± 0.8

7.6 ± 3.8

3.0 ± 1.0

2.1 ± 0.3

22.6 ± 0.6

77.4 ± 13.7

0.4 ± 0.3

Mibefradil**

6.8 ± 0.0b

70.2 ± 0.0a

1.0 ± 0.0b

0.0 ± 0.0b

30.0 ± 0.0b

0.0 ± 0.0b

0.1 ± 0.0b

1.4 ± 0.0b

98.6 ± 0.0a

0.01 ± 0.0b

Voriconazile*

114.0 ± 0.0a

1.2 ± 0.0b

7.7 ± 0.0a

661.2 ± 0.0a

49.5 ± 0.0a

160 ± 0.0a

99.1 ± 0.0a

87.0 ± 0.0a

13.0 ± 0.0b

6.7 ± 0.0a

Metronidazole**

0.45 ± 0.1b

0.6 ± 0.3b

0.7 ± 0.3b

−1.1 ± 1.1b

0.2 ± 0.0b

2.1 ± 1.9

3.1 ± 0.9a

54.6 ± 2.3a

45.4 ± 1.9b

1.2 ± 0.1a

Isoniazid**

30.9 ± 0.0a

1.70 ± 0.0b

2.5 ± 0.0a

27.8 ± 0.0a

13.4 ± 0.0a

46.3 ± 0.0a

18.5 ± 0.0b

60.0 ± 0.0a

40.0 ± 0.0b

1.5 ± 0.0a

Puromicin**

193.9 ± 0.0a

0.04 ± 0.0b

0.0 ± 0.0b

0.0 ± 0.0b

84.2 ± 0.0a

0.0 ± 0.0b

0.9 ± 0.0b

0.0 ± 0.0b

100 ± 0.0a

0.0 ± 0.0b

Phenytoin*

18.1 ± 9.9a

50.2 ± 40.8a

0.5 ± 0.5b

0.1 ± 0.1b

7.9 ± 4.3

0.2 ± 0.0b

0.2 ± 0.1b

0.8 ± 0.3b

99.2 ± 0.3a

0.01 ± 0.0b

Thiopental*

0.9 ± 0.1b

22.0 ± 2.0a

1.0 ± 0.0b

0.0 ± 0.0b

0.4 ± 0.0b

0.01 ± 0.0b

0.04 ± 0.0b

4.5 ± 0.4b

95.5 ± 0.4a

0.05 ± 0.0b

Thymidine*

2.5 ± 0.0b

45.5 ± 0.0a

1.0 ± 0.0b

0.0 ± 0.0b

1.1 ± 0.0b

0.1 ± 0.0b

0.1 ± 0.0b

2.1 ± 0.0b

97.9 ± 0.0a

0.02 ± 0.0b

Thymine*

2.6 ± 0.0b

82.5 ± 0.0a

1.0 ± 0.0b

0.0 ± 0.0b

1.1 ± 0.0b

0.03 ± 0.0b

0.03 ± 0.0b

1.2 ± 0.0b

98.8 ± 0.0a

0.01 ± 0.0b

Fluorouracil*

2.2 ± 0.0b

39.8 ± 0.0a

1.0 ± 0.0b

0.0 ± 0.0b

0.9 ± 0.0b

0.1 ± 0.0b

0.1 ± 0.0b

2.5 ± 0.0b

97.5 ± 0.0a

0.03 ± 0.0b

Tylosin*

0.02 ± 0.0b

0.4 ± 0.0b

0.6 ± 0.0b

0.01 ± 0.0b

0.01 ± 0.0

0.03 ± 0.0

0.05 ± 0.0

61.1 ± 0.0

39.0 ± 0.0b

1.6 ± 0.0a

  1. Keys: * = Enzyme inducer; ** = Enzyme inhibitor; a = significantly higher (P < 0.05); b = significantly lower (p < 0.05); 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 and unsaturation