Chemical Properties
White to Off-White Solid
Originator
Ajan,Kettelhack Riker,W. Germany,1976
Uses
A cyclized analog of orphenadrine and diphenhydramine; representative of a new class of centrally acting skeletal muscle relaxants, the benzoxazocines. Analgesic; antidepressant.
Manufacturing Process
The starting material is prepared by reacting 2-benzoylbenzoic acid with
thionyl chloride and then with 2-methylaminoethanol. 20.0 grams (0.07 mol)
of N-(2-hydroxyethyl)-N-methyl-o-benzoylbenzamide is suspended in 100 ml
tetrahydrofuran and then slowly added in small portions to a solution of 5.5
grams (0.14 mol) of lithium aluminum hydride in 150 ml tetrahydrofuran with
cooling and stirring. The mixture is then refluxed for 18 hours, cooled and
then to it is successively added 5.5 ml water, 5.5 ml of 3.75 N sodium
hydroxide and 16 ml water. After removal of precipitated salts by filtration, the
solution remaining is concentrated under reduced pressure and the residue
dried to yield 19.5 grams of crude product. Yield after conversion to the
hydrochloride salt and recrystallization is 17.0 grams (89%), MP 128° to
133°C.
5-methyl-1-phenyl-1,3,4,6-tetrahydro-5H-benz[f] -2,5-oxazocine is prepared
as follows. 3.0 grams (0.011 mol) of 2-([N-(2-hydroxyethyl)-Nmethyl]amino)methylbenzhydrol, prepared as described above, 3.0 grams ptoluenesulfonic acid and 15 ml benzene are heated together with stirring until
all the benzene is distilled off. The residual oil is heated to 105°C and held at
this temperature for 1 hour, then cooled and dissolved in 30 ml water. This
aqueous solution is then basified to pH 10.0 with 12 N sodium hydroxide,
extracted with ether, and the extracts washed with water, dried over
anhydrous sodium sulfate and the solvent removed under reduced pressure.
The 2.26 grams (81%) oil remaining is converted to the hydrochloride salt, MP
238° to 242°C.
Brand name
Acupan (3M
Pharmaceuticals).
Therapeutic Function
Muscle relaxant, Antidepressant
Biochem/physiol Actions
Nefopam is a centrally-acting analgesic drug of the benzoxazocine chemical class. Nefopam is a non-opioid, but has a potentiating effect on morphine and other opioids. Its mechanism of action is not certain, but may involve its action as a dopamine/serotonin/norepinephrine reuptake inhibitor.
Clinical Use
Analgesic for moderate pain
Drug interactions
Potentially hazardous interactions with other drugs
Antidepressants: avoid MAOIs; tricyclics possibly
increased risk of side effects.
Metabolism
Extensively metabolised in the liver to produce active
metabolites.
It is mainly excreted in the urine. About 8% of a dose is
excreted via the faeces.
