PEth Half-Life Calculator

This peth half-life calculator is used to estimate the time it takes for the concentration of Phosphatidylethanol (PEth) in the blood to reduce by half.

PEth is a direct alcohol biomarker formed in the presence of ethanol, making it useful for detecting alcohol consumption.

For example, if an individual’s initial PEth level is 400 ng/mL and the calculator estimates a half-life of 4 days, after 4 days, the PEth level would be approximately 200 ng/mL.

Initial PEth Level (ng/mL)	Half-Life (days)	Time Elapsed (days)	Calculated PEth Level (ng/mL)
800	5	10	200
600	7	14	150
1200	6	18	150
400	8	16	100
1000	4	12	125
900	5	15	112.5
500	6	12	125
700	7	21	87.5
300	8	24	18.75
1100	4	20	68.75
1500	6	30	93.75
2500	5	25	78.125
350	7	14	87.5
450	8	32	11.25

PEth Half-Life Formula

The PEth half life formula is based on the principle of exponential decay:

C(t) = C₀ * (1/2)^(t/t₁/₂)

Where:

C(t) is the concentration at time t

C₀ is the initial concentration

t is the elapsed time

t₁/₂ is the half-life

If the initial PEth level is 800 ng/mL and the half-life is 5 days, after 10 days:

C(10) = 800 * (1/2)^(10/5) = 800 * 0.25 = 200 ng/mL

What is PEth Half-Life?

PEth half-life refers to the time required for the concentration of PEth in the blood to decrease by 50%. This concept is crucial for understanding how long PEth remains detectable after alcohol consumption ceases.

The half-life of PEth can vary depending on individual factors and the specific PEth homolog. Generally, the half-life of PEth is estimated to be between 4 to 12 days.

An individual’s PEth level is 600 ng/mL and the half-life is 6 days, the expected levels over time would be:

Day 0: 600 ng/mL
Day 6: 300 ng/mL
Day 12: 150 ng/mL
Day 18: 75 ng/mL

How Long Does It Take for PEth to Go Down?

It may take 5-6 weeks or more for PEth to become undetectable, depending on the test’s sensitivity.

The time for PEth levels to decrease depends on various factors, including initial concentration, individual metabolism, and alcohol consumption patterns. Generally, it takes multiple half-lives for PEth to reach undetectable levels.

For instance, assuming a half-life of 7 days and an initial level of 1000 ng/mL:

After 1 week: ~500 ng/mL
After 2 weeks: ~250 ng/mL
After 3 weeks: ~125 ng/mL
After 4 weeks: ~62.5 ng/mL

What is the Half-Life of PEth 16:0/18:1?

PEth 16:0/18:1 is a specific homolog of PEth often used in alcohol biomarker testing. Its half-life is typically around 4-10 days, with some studies suggesting an average of about 7 days.

An individual’s PEth 16:0/18:1 level is 400 ng/mL and the half-life is 7 days:

Day 0: 400 ng/mL
Day 7: 200 ng/mL
Day 14: 100 ng/mL
Day 21: 50 ng/mL

What is Half-Time for PEth?

The terms “half-life” and “half-time” are often used interchangeably when discussing PEth. Both refer to the time required for the PEth concentration to decrease by 50%.

The half-time of PEth is 8 days and the initial concentration is 320 ng/mL:

After 8 days: 160 ng/mL
After 16 days: 80 ng/mL
After 24 days: 40 ng/mL

PEth Level of 1000 ng/mL

A PEth level of 1000 ng/mL is considered very high and indicates significant alcohol consumption. Using a half-life of 6 days, here’s how the level might decrease over time:

Day 0: 1000 ng/mL
Day 6: 500 ng/mL
Day 12: 250 ng/mL
Day 18: 125 ng/mL
Day 24: 62.5 ng/mL
Day 30: 31.25 ng/mL

References

Gnann, H., et al. (2012). Identification of 48 homologues of phosphatidylethanol in blood by LC-ESI-MS/MS. Analytical and Bioanalytical Chemistry, 402(7), 2251-2261. PubMed
Helander, A., & Zheng, Y. (2009). Molecular species of the alcohol biomarker phosphatidylethanol in human blood measured by LC-MS. Clinical Chemistry, 55(7), 1395-1405. Clinical Chemistry
Ulwelling, A., & Smith, K. (2018). The PEth test in the detection of chronic alcohol use: a meta analysis. Alcoholism: Clinical and Experimental Research, 42(9), 1703-1713. Wiley Online Library

Related Tools:

PEth Half-Life Calculator – Calculate Peth Level