Urine Excretion of Benzoylecgonine Following Cocaine Use

 

A nomogram for excretion of benzoylecgonine versus time based on dose taken is shown on page 245 of Ambre (1985). The peak excretion is reached about 5-6 hours after use. Extrapolating the elimination line back to time = 0, the following equations can be used to approximate excretion.

 

LOG10(benzoylecgonine level in urine after 10 mg dose in µg/mL) =

= (-0.04033 * (hours since taken)) + 0.9275

 

LOG10(benzoylecgonine level in urine after 50 mg dose in µg/mL) =

= (-0.041059 * (hours since taken)) + 1.6522

 

LOG10(benzoylecgonine level in urine after 100 mg dose in µg/mL)=

= (-0.040934 * (hours since taken)) + 1.9493

 

LOG10(benzoylecgonine level in urine after 500 mg dose in µg/mL) =

= (-0.04 * (hours since taken)) + 2.628

 

LOG10(benzoylecgonine level in urine after 1000 mg dose in µg/mL) =

= (-0.04015 * (hours since taken)) + 2.935

 

The average slope of the lines is –0.0405.

Cocaine Dose in mg	Y-Intercept (t = 0)
10	0.9275
50	1.6522
100	1.9493
500	2.628
1,000	2.935

 

Y intercept in µg/mL =

= (0.9986 * LOG10(dose in mg)) – 0.05819

 

Cocaine Dose in mg	X-Intercept (0 µg/mL)
10	23 hours
50	40.24 hours
100	47.62 hours
500	65.7 hours
1,000	73.1 hours

 

Using JMP, the X-intercept can be predicted based on dose in mg:

 

X intercept in hours =

= (25.165 * LOG10 (dose in mg)) – 2.3

 

If a dose of D mg cocaine is ingested at one sitting, then the level of benzoylecgonine in the urine can be predicted over time, including the time when no more will be detected in the urine.

 

LOG10(urine excretion in µg/mL of benzoylecgonine) =

= (-0.0405 * (hours since use)) + (Y-intercept for dose) =

= (-0.0405 * (hours since use)) + (0.9986 * LOG10(dose in mg)) – 0.05819

 

urine excretion in µg/mL of benzoylecgonine =

= 10 ^ ((-0.0405 * (hours since use)) + (0.9986 * LOG10(dose in mg)) – 0.05819)

 

time when benzoylecgonine no longer detected in hours from dose =

= X intercept =

= (25.165 * LOG10 (dose in mg)) – 2.3

 

If A amount of benzoylecgonine is present in the urine H hours after use, then the amount taken can be estimated.

 

LOG10(A) =

= (-0.0405 * (H hours)) + (Y-intercept for dose) =

= (-0.0405 * (H hours)) + (0.9986 * LOG10(dose in mg)) – 0.05819

 

LOG10(dose in mg)) =

= (LOG10(A) + (0.0405 * (H hours)) + 0.05819) / 0.9986

 

dose in mg =

= 10 ^ ((LOG10(A) + (0.0405 * (H hours)) + 0.05819) / 0.9986)