The edition · Clinical Pharmacology
Clozapine levels: more is not obviously better, and side effects climb sooner than benefit
A dose-response meta-analysis of 34 studies places the turning points for several clozapine harms below those for symptom response. Also: cenobamate's two-way effect on brivaracetam, levetiracetam kinetics in cooled neonates, and a compounded semaglutide recall.
The edition in brief
Today's clinical pharmacology edition closes on a dose-response meta-analysis of 34 studies and 134,111 participants relating plasma clozapine levels to outcomes. Exploratory turning points for symptom change sat at about 535 ng/mL on one rating scale and 898 ng/mL on another, while those for salivary hypersecretion (225), blood dyscrasia (357), EEG abnormality or seizures (452) and tachycardia (503 ng/mL) were lower; the authors stress these are not targets or thresholds. A retrospective cohort of 213 patients found cenobamate raised brivaracetam levels by 32% at low doses but lowered them by 21% at high doses. A population pharmacokinetic study in 15 cooled neonates with hypoxic-ischaemic encephalopathy found levetiracetam clearance rose with creatinine clearance and serum sodium. The FDA lists class II recalls of compounded semaglutide with cyanocobalamin for lack of sterility assurance. The pearl covers the events that should prompt a clozapine level.
Cenobamate and brivaracetam: levels rose at low cenobamate doses and fell at high ones
When adding cenobamate to brivaracetam, expect levels to rise during early titration and fall at higher doses; consider level checks at both points.
Levetiracetam in cooled neonates: clearance tracked renal function and serum sodium
In cooled neonates with encephalopathy, factor renal function into levetiracetam maintenance dosing.
FDA class II recall: compounded semaglutide with cyanocobalamin, sterility not assured
Ask patients using injectable incretins about the source, and treat compounded combinations with B12 as unlicensed products of uncertain sterility.
When to check a clozapine level
Recheck clozapine levels whenever smoking status changes, a CYP1A2 inhibitor is added, or the patient becomes acutely unwell.
Clozapine concentration and response: several harms turn up at lower levels than benefit
Guide clozapine dosing by individual plasma levels and be cautious about pushing high concentrations, where harm may rise faster than benefit.
Read the rest in the app
You have read your two free briefings this month. The app carries all 27 specialties, every morning, free — and this one is waiting in it.
Scan to keep reading on your phone. No account needed to start.
Tomorrow morning, before your first patient
One edition a day for clinical pharmacology, written by the desk, every claim tied to its paper. Six minutes.
Get the app — free