Propofol

🧬 Receptor activity

Target	Action	Affinity	Source
5-hydroxytryptamine receptor 2B	—	Ki 3499 nM	CHEMBL
5-hydroxytryptamine receptor 2C	—	Ki 6051 nM	CHEMBL
Sodium-dependent noradrenaline transporter	—	Ki 9316 nM	CHEMBL
Carbonic anhydrase 2	—	Ki 19500 nM	CHEMBL
Unchecked	—	Ki 22994 nM	CHEMBL
Carbonic anhydrase 1	—	Ki 98900 nM	CHEMBL

Mechanism of action

The action of propofol involves a positive modulation of the inhibitory function of the neurotransmitter gama-aminobutyric acid (GABA) through GABA-A receptors.

Pharmacodynamics

Propofol is a sedative-hypnotic agent for use in the induction and maintenance of anesthesia or sedation. Intravenous injection of a therapeutic dose of propofol produces hypnosis rapidly with minimal excitation, usually within 40 seconds from the start of an injection (the time for one arm-brain circulation).

Pharmacokinetics

Half-life

Initial distribution phase t1/2α=1.8-9.5 minutes. Second redistirubtion phase t1/2β=21-70 minutes. Terminal elimination phase t1/2γ=1.5-31 hours.
Terminal elimination half-life is 3 to 12 hours; prolonged administration may result in longer duration.
...The first-stage elimination half-life (t1/2 beta) of propofol /SRP: administered mixed with lidocaine/ in children was shorter (mean 9.3 +/- 3.8 (s.d.) min) than the values found in adults. This pharmacokinetic alteration may have clinical significance following repeated administration or continuous infusion of propofol.
An intravenous dose of 14C-propofol (0.47 mg/kg) /was/ administered to six male volunteers... . ...The half-lives of the first and second exponential phases, mean values 5 min and 97 min respectively, varied widely among subjects.

Absorption

Rapid - time to onset of unconsciousness is 15-30 seconds, due to rapid distribution from plasma to the CNS. Distribution is so rapid that peak plasma concentrations cannot be readily measured. Duration of action is 5-10 minutes.
It is chiefly eliminated by hepatic conjugation to inactive metabolites which are excreted by the kidney.
60 L/kg [healthy adults]
23 - 50 mL/kg/min
1.6 - 3.4 L/min [70 Kg adults]
The initial apparent volume of distribution is 13 to 76 L/kg.

Metabolism

Hepatically metabolized mainly by glucuronidation at the C1-hydroxyl. Hydroxylation of the benzene ring to 4-hydroxypropofol may also occur via CYP2B6 and 2C9 with subsequent conjugation to sulfuric and/or glucuronic acid. Hydroxypropofol has approximately 1/3 of hypnotic activity of propofol.
Hepatic; rapidly undergoes glucuronide conjugation to inactive metabolites. An unidentified route of extrahepatic metabolism may also exist, suggested by the fact that propofol clearance exceeds estimated hepatic blood flow.
To determine the cytochrome P450 (CYP) isoforms involved in the oxidation of propofol by human liver microsomes. The rate constant calculated from the disappearance of propofol in an incubation mixture with human liver microsomes and recombinant human CYP isoforms was used as a measure of the rate of metabolism of propofol. The correlation of these rate constants with rates of metabolism of CYP isoform-selective substrates by liver microsomes, the effect of CYP isoform-selective chemical inhibitors and monoclonal antibodies on propofol metabolism by liver microsomes, and its metabolism by recombinant human CYP isoforms were examined. The mean rate constant of propofol metabolism by liver microsomes obtained from 6 individuals was 4.2 (95% confidence intervals 2.7, 5.7) nmol/min/mg protein. The rate constants of propofol by microsomes were significantly correlated with S-mephenytoin N-demethylation, a marker of CYP2B6 (r=0.93, P<0.0001), but not with the metabolic activities of other CYP isoform-selective substrates. Of the chemical inhibitors of CYP isoforms tested, orphenadrine, a CYP2B6 inhibitor, reduced the rate constant of propofol by liver microsomes by 38% (P<0.05), while other CYP isoform-selective inhibitors had no effects. Of the recombinant CYP isoforms screened, CYP2B6 produced the highest rate constant for propofol metabolism (197 nmol/min/nmol P450). An antibody against CYP2B6 inhibited the disappearance of propofol in liver microsomes by 74% /and SRP: reduced in vitro metabolism by blocking CYP 2B6/. Antibodies raised against other CYP isoforms had no effect on the metabolism of propofol. CYP2B6 is predominantly involved in the oxidation of propofol by human liver microsomes.
Propofol has known human metabolites that include (2S,3S,4S,5R)-6-[2,6-Di(propan-2-yl)phenoxy]-3,4,5-trihydroxyoxane-2-carboxylic acid and 4-hydroxy-propofol.
Propofol is rapidly distributed into peripheral tissues after absorption. It is highly protein bound in vivo and is metabolised by conjugation in the liver. Propofol is metabolized mainly by glucuronidation by uridine diphosphate-glucuronosyltransferases (UGTs) and by hydroxylation by CYP2B6 and CYP2C enzymes. The enzymes SULT1A1 and NQO1 participate in later steps in propofol metabolism. An unidentified route of extrahepatic metabolism may also exist, suggested by the fact that propofol clearance exceeds estimated hepatic blood flow. (L1002, A600, A304). Propofol is hepatically metabolized mainly by glucuronidation at the C1-hydroxyl. Hydroxylation of the benzene ring to 4-hydroxypropofol may also occur via CYP2B6 and 2C9 with subsequent conjugation to sulfuric and/or glucuronic acid. Hydroxypropofol has approximately 1/3 of hypnotic activity of propofol.
Route of Elimination: It is chiefly eliminated by hepatic conjugation to inactive metabolites which are excreted by the kidney.
Half Life: Initial distribution phase t1/2α=1.8-9.5 minutes. Second redistirubtion phase t1/2β=21-70 minutes. Terminal elimination phase t1/2γ=1.5-31 hours.

Protein binding

95 to 99%, primarily to serum albumin and hemoglobin