Levetiracetam Unit Converter
Levetiracetam Unit Converter
Convert levetiracetam between µg/mL and µmol/L, and see why this renally cleared antiepileptic rarely needs routine monitoring outside pregnancy, renal impairment and dialysis.
Levetiracetam converter
Mass ⇄ molarLevetiracetam 25 µg/mL
Formula and conversion factor
µg/mL = µmol/L ÷ 5.8751
- 5.8751
- derived from the molecular weight of levetiracetam, 170.21 Da (1000 ÷ 170.21)
- mg/L
- numerically identical to µg/mL
- renal clearance
- the dose, not the level, is the usual lever adjusted for renal function and haemodialysis
Worked example
Levetiracetam 25 µg/mL
25 × 5.8751 = 146.9 µmol/L
= 25 mg/L
Levetiracetam's pharmacokinetic profile
| Property | Levetiracetam |
|---|---|
| Protein binding | Minimal (< 10%) |
| Hepatic metabolism | Negligible — cleared mainly unchanged renally |
| CYP interactions | None of clinical significance |
| Haemodialysis | Substantially removed — supplementary dose needed after each session |
An antiepileptic that mostly monitors itself
Levetiracetam is pharmacokinetically unusual among antiepileptic drugs, and that is largely why it has become so widely used. Protein binding is minimal, so displacement interactions are not a concern; hepatic metabolism is negligible, since most of the drug is cleared unchanged or through a non-hepatic hydrolysis pathway; and it has no cytochrome P450 interactions of clinical significance in either direction, so it can generally be added to or removed from a regimen without needing to adjust other drugs.
What it does depend on is the kidney. Levetiracetam is cleared almost entirely by renal excretion, so the dose must be adjusted for creatinine clearance in renal impairment, and it is substantially removed by haemodialysis — a patient on dialysis needs a supplementary dose after each session to replace what the dialyser has cleared.
Routine monitoring is not required for most patients, since dosing is generally guided by response rather than by level. It becomes useful in specific situations: in pregnancy, where clearance rises considerably — levetiracetam is among the antiepileptics most affected by pregnancy-related pharmacokinetic change — and levels can fall enough to threaten seizure control; in renal impairment, to confirm an adjusted dose is achieving an adequate level; and to assess adherence when seizure control is unexpectedly poor despite a seemingly adequate prescribed dose.
It is worth being candid that the commonly quoted reference range is wide and only weakly evidence-based — it describes concentrations seen in treated populations rather than a tightly validated therapeutic window, so a level outside it is a prompt to review the clinical picture, not an automatic trigger for a dose change.
Frequently asked questions
How do I convert levetiracetam from µg/mL to µmol/L?
Multiply by 5.8751. A level of 25 µg/mL is 146.9 µmol/L. The factor comes from levetiracetam’s molecular weight of 170.21 Da.
Does levetiracetam need routine level monitoring?
Not usually. It is dosed to clinical response rather than a target level. Monitoring is most useful in pregnancy, renal impairment or dialysis, and to check adherence.
Why does levetiracetam need a supplementary dose after dialysis?
It is cleared renally and is substantially removed by haemodialysis, so a supplementary dose is given after each session to replace what was removed.
Does levetiracetam interact with other antiepileptics?
Not significantly. It has minimal protein binding, negligible hepatic metabolism and no clinically significant cytochrome P450 interactions, which is unusual among antiepileptic drugs.
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References
- Patsalos PN. Clinical pharmacokinetics of levetiracetam. Clin Pharmacokinet. 2004;43(11):707–24.
- Patsalos PN et al. Antiepileptic drugs — best practice guidelines for therapeutic drug monitoring: ILAE position paper. Epilepsia. 2008;49(7):1239–76.