Population pharmacokinetics of S-ketamine and norketamine in healthy volunteers after intravenous and oral dosing

• Low-dose ketamine is a lucrative therapeutic approach in cancer pain, perioperative treatment of pain, and management of treatment-resistant depression. The analgesic potency of its main metabolite norketamine is thought to be one third that of ketamine. However, few studies exist on the pharmacokinetics of orally administered S-ketamine. In our study, 11 healthy volunteers received S-ketamine 0.25 mg/kg orally and 0.125 mg/kg intravenously. S-ketamine and norketamine concentrations were measured up to 23.5 h post-dose. A population pharmacokinetic model was built to describe S-ketamine and norketamine pharmacokinetics. A three-compartment model for both S-ketamine and norketamine best described the data. To accommodate for the extensive formation of norketamine after oral S-ketamine, a separate presystemic absorption-phase component was included in addition to its systemic formation. The oral bioavailability of S-ketamine was low, 8 % (11 % interindividual variability), and its clearance was high, 95 L/h/70 kg (13 % interindividual variability). Simulations suggested that after oral dosing, norketamine AUC at steady state is 16.5 times higher than that of S-ketamine. Given that the analgesic effect of S-ketamine is due to both S-ketamine and norketamine, relatively small oral doses of S-ketamine can be assumed to be a feasible alternative to repeated intravenous dosing, for example in the setting of chronic pain.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Farmaceutiska vetenskaper (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Pharmaceutical Sciences (hsv//eng)

Nyckelord

Ketamine

S-ketamine

Norketamine

Population pharmacokinetics

CYP2B6

CYP3A4

First-pass effect

Well-stirred model

Publikations- och innehållstyp

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