According to #grok..

Fentanyl is a potent opioid, and even small amounts can be lethal, especially if the individual has no opioid tolerance. Levels of 11 ng/mL are significant; for comparison, in some cases, levels above 10 ng/mL have been associated with overdose, though this can vary widely based on individual tolerance, rate of administration, and presence of other drugs.

Methamphetamine levels around 19 ng/mL can also be quite high, especially if the individual has underlying health issues or has used other substances concurrently. Methamphetamine toxicity can lead to severe cardiovascular effects, hyperthermia, and seizures, which could be fatal.

THC and its metabolites are less likely to be directly lethal at these levels, but they contribute to the overall intoxication profile, potentially exacerbating the effects of other substances present.

4-ANPP and Norferntanyl are metabolites of fentanyl and might not be lethal on their own at these concentrations, but they indicate fentanyl metabolism and could contribute to overall opioid effects.

The presence of multiple drugs, especially opioids and stimulants, increases the risk of a fatal outcome due to drug synergy, where the combined effect of substances is greater than the sum of their individual effects. This can lead to respiratory depression, cardiovascular collapse, or other life-threatening complications.

In summary, the levels of fentanyl and methamphetamine found could indeed be potentially lethal, especially in combination with each other and considering any individual's health status or tolerance to these substances. The presence of THC would add to the complexity of the overall drug interaction.