Sampling considerations and selected pharmacokinetic parameters for analgesics monitoring.1
| Analgesics | Chirality | Sample | Half-life | Excreted in urine | Time to peak | Therapeutic dose | Therapeutic concentrations | Time of sampling |
|---|---|---|---|---|---|---|---|---|
| Salicylate (Acetylsalicylic acid) | NA2 | Serum, plasma (heparin or EDTA), urine, saliva, synovial fluids | 3–20 h (∼ dose) (saturation kinetics) (10–30 min, ASA) | 5% (SA) | 1–2 h3 | 0.5–1 g4 5–6 g6 | 20–100 mg/L4 5 100–250 mg/L6 | After acute OD: on presentation, then every 2 h until peak, and every 4–6 h thereafter |
| Diflunisal | NA | Serum or plasma | 5–12 h | <10% | 2–3 h | 250–500 mg | 50–200 mg/L | NA |
| Acetaminophen | NA | Serum/plasma (EDTA),7 urine, CSF | 1–3 h 3.2 h | <5% | 0.5–1.0 h>4 h for OD8 4 h | 0.5–1 g | 10–20 mg/L >Plasma | 4 h after a single acute ingestion; 4–8 h following ER OD; 2 levels needed, if co-ingested, to assure complete absorption |
| (S)-(+)-Ibuprofen | Eutomer | Serum, plasma, | 1–3 h | <10% | 1–2 h | 200–800 mg | 15–30 mg/L | NA |
| (R)-(−)-Ibuprofen | Distomer | urine | ||||||
| (S)-(+)-Naproxen | Eutomer | Serum, plasma, | 9–22 h | 10% | 1–4 h | 275–1500 mg | 50–100 mg/L | NA |
| urine | ||||||||
| (+/−)-Tramadol | ? | Serum, plasma, | 6.3 h | 30% | 2–3 h | 50–400 mg | NE (300 μg/L, Cmax | NA |
| urine | for 100-mg dose) | |||||||
| (+/−)-M1-tramadol | ? | 7.4 h | <60% | NE (55μg/L, Cmax | ||||
| metabolite9 | for 100-mg dose) |