Chemical Properties
White Crystalline Solid
Uses
A compound which inhibits burst firing without affecting normal neuronal excitability
Uses
The (S)-enantiomer of Etiracetam (E932970) and the ethyl analog of Piracetam (P500800). Used as an anticonvulsant.
Uses
The (S)-enantiomer of the ethyl analog of Piracetam. Used as an anticonvulsant.
Uses
Used as adjunctive therapy in the treatment of partial onset seizures in adults and children 4 years of age and older with epilepsy.
Definition
ChEBI: A pyrrolidinone and carboxamide that is N-methylpyrrolidin-2-one in which one of the methyl hydrogens is replaced by an aminocarbonyl group, while another is replaced by an ethyl group (the S enantiomer). An anticonvulsa
t, it is used for the treatment of epilepsy in both human and veterinary medicine.
Manufacturing Process
(a) Preparation of the (R)-α-methyl-benzylamine salt of (S)-α-ethyl-2-oxo-1-
pyrrolidineacetic acid
8.7 kg (50.8 moles) of racemic ()-α-ethyl-2-oxo-1-pyrrolidineacetic acid are
suspended in 21.5 liters of anhydrous benzene in a 50 liter reactor. To this
suspension is added gradually a solution containing 3.08 kg (25.45 moles) of
(R)-(+)-α-methyl-benzylamine and 2.575 kg (25.49 moles) of triethylamine in
2.4 liters of anhydrous benzene. This mixture is then heated to reflux
temperature until complete dissolution. It is then cooled and allowed to
crystallize for a few hours. 5.73 kg of the (R)-α-methyl-benzylamine salt of
(S)-α-ethyl-2-oxo-1-pyrrolidineacetic acid are thus obtained. Melting point:
148°-151°C. Yield: 77.1%.
This salt may be purified by heating under reflux in 48.3 liters of benzene for
4 hours. The mixture is cooled and filtered to obtain 5.040 kg of the desired
salt. Melting point: 152°-153.5°C. Yield: 67.85%.
(b) Preparation of (S)-α-ethyl-2-oxo-1-pyrrolidineacetic acid
5.04 kg of the salt obtained in (a) above are dissolved in 9 liters of water. 710
g of a 30% sodium hydroxide solution are added slowly so that the pH of the
solution reaches 12.6 and the temperature does not exceed 25°C. The
solution is stirred for a further 20 minutes and the α-methylbenzylamine
liberated is extracted with a total volume of 18 liters of benzene. The aqueous
phase is then acidified to a pH of 1.1 by adding 3.2 liters of 6 N hydrochloric
acid. The precipitate formed is filtered off, washed with water and dried. The
filtrate is extracted repeatedly with a total volume of 50 liters of
dichloromethane. The organic phase is dried over sodium sulfate and filtered
and evaporated to dryness under reduced pressure. The residue obtained after
the evaporation and the precipitate isolated previously, are dissolved together
in 14 liters of hot dichloromethane. The dichloromethane is distilled and
replaced at the distillation rate, by 14 liters of toluene from which the product
crystallizes. The mixture is cooled to ambient temperature and the crystals
are filtered off to obtain 2.78 kg of (S)-α-ethyl-2-oxo-1-pyrrolidineacetic acid.
Melting point: 125.9°C. [α]D20 = -26.4° (c = 1, acetone). Yield: 94.5%.
(c) Preparation of (S)-α-ethyl-2-oxo-1-pyrrolidineacetamide
34.2 g (0.2 mole) of (S)-α-ethyl-2-oxo-1-pyrrolidineacetic acid are suspended
in 225 ml of dichloromethane cooled to -30°C. 24.3 g (0.24 mole) of
triethylamine are added dropwise over 15 minutes. The reaction mixture is
then cooled to -40°C and 24.3 g (0.224 mole) of ethyl chloroformate are
added over 12 minutes. Thereafter, a stream of ammonia is passed through
the mixture for 4 ? hours. The reaction mixture is then allowed to return to
ambient temperature and the ammonium salts formed are removed by
filtration and washed with dichloromethane. The solvent is distilled off under
reduced pressure. The solid residue thus obtained is dispersed in 55 ml
toluene and the dispersion is stirred for 30 minutes and then filtered. The
product is recrystallized from 280 ml of ethyl acetate in the presence of 9 g of
0.4 nm molecular sieve in powder form 24.6 g of (S)-α-ethyl-2-oxo-1-
pyrrolidineacetamide are obtained. Melting point: 115°-118°C. [α]D25 = -89.7°
(c = 1, acetone). Yield: 72.3%.
Therapeutic Function
Antiepileptic, Nootropic
Biological Functions
Levetiracetam (Keppra) has recently been approved for
the treatment of partial-onset seizures. It appears to be
safe and effective; its exact therapeutic profile has yet to
be determined. It does not appear to share any of the
mechanisms of action of agents that have been discussed
to this point. It does have a highly specific brain
binding site, but the significance of this observation to
its mechanism of action has not been elucidated.
General Description
LEV is an analog of the nootropic agent, piracetam. Onlythe S-isomer has any anticonvulsant activity. Unlike piracetam, LEV does not have any affinity for the AMPA receptor thereby has no nootropic activity forthe treatment of Alzheimer disease. LEV also has no affinityfor GABA receptors, BZD receptors, the various excitatoryamino acid related receptors, or the voltage-gated ionchannels.For this reason, its mechanism of anticonvulsantaction remains unclear, but it appears to exert itsantiepileptic action by modulating kainite/AMPA-inducedexcitatory synaptic currents, thus decreasing membraneconductance.Furthermore, the anticonvulsant activity ofthis drug appears to be mediated by the parent moleculerather than by its inactive metabolite,(S)-α-ethyl-2-oxo-1-pyrrolidineacetic acid (i.e., via the hydrolysis of amidegroup).Like gabapentin, LEV has few drug interactionswith other AEDs thereby can be used in combination to treatrefractory epilepsy.
Biological Activity
Antiepileptic that displays distinctive properties from conventional antiepileptic drugs. Displays potent seizure protection in animal models of chronic epilepsy but lacks activity in acute seizure models. Binds synaptic vesicle protein 2A (SV2A) and inhibits Na + -dependent Cl - /HCO 3 - exchange.
Biochem/physiol Actions
Levetiracetam is a pyrrolidine with antiepileptic activity. Stereoselective binding of levetiracetam was confined to synaptic plasma membranes in the central nervous system with no binding occurring in peripheral tissue. Levetiracetam inhibits burst firing without affecting normal neuronal excitability, which suggests that it may selectively prevent hyper-synchronization of epileptiform burst firing and propagation of seizure activity.
Mechanism of action
The mechanism of action for S-(–)-levetiracetam is unknown. It does not appear to interact with any of the recognized
excitatory or inhibitory neural mechanism. A CNS-specific binding site for S-(–)-levetiracetam has been identified as the
synaptic vesicle protein (SV2A). Knockout animals without SV2A proteins accumulated presynaptic Ca2+ during consecutive
action potentials that destabilized synaptic circuits and induced epilepsy. Thus, it appears that SV2A plays a major role in the
antiepileptic properties of S-(–)-levetiracetam, which acts by modulating the function of SV2A and the regulation of
Ca2+ mediated synaptic transmission. These data support previous indications that S-(–)-levetiracetam possesses a mechanism
of action distinct from that of other antiepileptic drugs. Three SV2 isoforms (SV2A, SV2B, and SV2C) have been identified, each
of which has a unique distribution in brain, suggesting synapse-specific functions as well as antagonism of neuronal
synchronization.
Pharmacokinetics
S-(–)-levetiracetam displays rapid and complete absorption, although food slows the rate but not the extent of absorption. It exhibits linear pharmacokinetics and is minimally protein bound. Approximately 60% of an oral dose is excreted into the
urine unchanged and 24 to 30% as its carboxylic acid metabolite, with an elimination half-life in adults of approximately 7
hours. Although S-(–)-levetiracetam is not metabolized by hepatic CYP450, UGT, or epoxide hydrolase, it is esterase
hydrolyzed to its carboxylic acid metabolite (loss of amido group), which is not affected by the hepatic metabolizing enzymes.
Clinical Use
S-(–)-levetiracetam is a pyrrolidone derivative unrelated to the structures of other AEDs. It is indicated as an adjunct in the
treatment of partial onset seizures in adults, and it has shown some benefit in clinical trials for generalized tonic-clonic
seizures (GTC) and myoclonic seizures in adults and children.
Side effects
The risk of clinically relevant drug interactions is minimal with S-(–)-levetiracetam, because it does not alter the
pharmacokinetics of coadministered drugs by inhibition or induction of hepatic enzymes. Toxic effects include mild to
moderate somnolence, asthenia, ataxia, and dizziness; these effects seldom require discontinuance. An increase in the
incidence of behavioral abnormalities in children and in adults having a previous history of neuropsychiatric problems has been
noted. Its use in the elderly or in patients with renal impairment will require an individualization of dose, and an additional
dose is needed after renal dialysis. Levetiracetam was associated with developmental toxicity in the offspring of pregnant
animals.
Veterinary Drugs and Treatments
Levetiracetam may be useful as a third antiseizure medication in
dogs that are not well controlled with phenobarbital and bromides
or when either bromides or phenobarbital are not tolerated. Some
evidence suggests that in dogs suffering from phenobarbital liver
toxicity, the addition of levetiracetam will allow reduction of their
phenobarbital dosage without increasing seizure frequency.
Levetiracetam may also be useful as add-on therapy in cats.
Drug interactions
Potentially hazardous interactions with other drugs
Alcohol: may produce a disulfiram-like reaction.
Phenytoin: increased levels of phenytoin have been
reported.
Warfarin: enhanced INR
References
1) Wright?et al.?(2013)?Clinical Pharmacology and Pharmacokinetics of Levetiracetam; Front. Neurol.?4?192
2) De Smedt?et al.?(2007)?Levetiracetam: the profile of a novel anticonvulsant drug – part I: preclinical data; CNS Drug Rev.?13?43
3) Klitgaard and Verdru (2007)?Levetiracetam: the first SV2A ligand for the treatment of epilepsy; Drug Discov.?21537
4) Lynch?et al.?(2004)?The synaptic vesicle protein SV2A is the binding site for the antiepileptic drug levetiracetam; Proc. Natl. Acad. Sci. USA?101?9861
5) Nagarkatti et al. (2008)?Levetiracetam inhibits both ryanodine and IP3 receptor activated calcium induced calcium release in hippocampal neurons in culture; Neurosci. Lett.?436?289
6) Bonnet?et al.?(2019)?Levetiracetam mediates subtle pH-shifts in adult human pyramidal cells via an inhibition of the bicarbonate-driven neuronal pH-regulation – Implications for excitability and plasticity modulation; Brain Res.?1710?146
