Flumazenil

Flumazenil is a competitive GABAA receptor antagonist, used in the treatment of benzodiazepine overdoses.

Signaling Pathways >> Membrane Transporter/Ion Channel >> GABA Receptor

Signaling Pathways >> Neuronal Signaling >> GABA Receptor

Research Areas >> Neurological Disease

Flumazenil interacts at the central benzodiazepine receptor to antagonize or reverse the behavioral, neurologic, and electrophysiologic effects of benzodiazepine agonists and inverse agonists. Flumazenil is of some benefit in hepatic encephalopathy, but until well-designed clinical trials are conducted, hepatic encephalopathy must be considered an investigational indication for flumazenil. Flumazenil has been shown to reverse sedation caused by intoxication with benzodiazepines alone or benzodiazepines in combination with other agents, but it should not be used when cyclic antidepressant intoxication is suspected[1]. Flumazenil (1 mg/kg) induces a strong anxiolytic effect in BALB/c mice tested in the elevated plus maze and light/dark test[2]. Flumazenil (10 mg/kg) effectively prevents the reduction produced by allopregnanolone in rats[3]. Flumazenil (5-20 mg/kg) antagonizes the anticonvulsant and adverse effects of diazepam but not GYKI 52466 in mice. Flumazenil slightly reduces the anticonvulsant activity of NBQX in the MES model but not in the PTZ test[4]. Flumazenil (3.0 mg/kg) blocks the changes withdrawal from chronic ethanol treatment, which leads to a decrease in open arm time and percent open arm entries[5].

Flumazenil is administered intraperitoneally in a volume of 10 mL/kg body weight 20 min before experimental testing. Two polyvinylchloride boxes (20×20×14 cm) covered with Plexiglas are connected by an opaque plastic tunnel (5×7×10 cm). One of these boxes is darkened. A light from a 100-W desk lamp 40 cm above the other box provided the only room illumination. This light level (300 lux) is chosen in order to avoid strain differences to be detected on time in the lit box (a measure of anxiety behaviour) in control animals. Indeed, in previous experiments, the BALB/c mice differ from C57BL/6 only in the high light condition. The subjects are individually tested in 5-min sessions between 1400 and 1700 hours. Mice are placed in the lit box to start the test session. The time spent in the lit box and the number of transitions from the dark box to the lit one are recorded after the first entry in the tunnel.

[1]. Hoffman EJ, et al. Flumazenil: a benzodiazepine antagonist. Clin Pharm. 1993 Sep;12(9):641-56; quiz 699-701.

[2]. Belzung C, et al. Flumazenil induces benzodiazepine partial agonist-like effects in BALB/c but not C57BL/6 mice. Psychopharmacology (Berl). 2000 Jan;148(1):24-32.

[3]. Fernandez-Guasti A, et al. Flumazenil blocks the anxiolytic action of allopregnanolone. Eur J Pharmacol. 1995 Jul 25;281(1):113-5.

[4]. Loscher W, et al. Effects of the non-NMDA antagonists NBQX and the 2,3-benzodiazepine GYKI 52466 on different seizure types in mice: comparison with diazepam and interactions with flumazenil. Br J Pharmacol. 1994 Dec;113(4):1349-57.

[5]. Moy SS, et al. Flumazenil blockade of anxiety following ethanol withdrawal in rats. Psychopharmacology (Berl). 1997 Jun;131(4):354-60.

(+)-Bicuculline | Picrotoxin | Aminooxyacetic acid hemihydrochloride | Riluzole | Baclofen | basmisanil | (R)-Baclofen | Etifoxine | Etomidate | Ginkgolide A | NS-11394 | 5alpha-Pregnan-3alpha-ol-20-one | CGP 52432 | L-655,708 | SAGE-217

MOLECULAR FORMULA :

C15-H14-F-N3-O3

MOLECULAR WEIGHT :

303.32

HEALTH HAZARD DATA

ACUTE TOXICITY DATA

TYPE OF TEST :

LDLo - Lowest published lethal dose

ROUTE OF EXPOSURE :

Intravenous

SPECIES OBSERVED :

Human - man

DOSE/DURATION :

5700 ng/kg/C

TOXIC EFFECTS :

Cardiac - cardiomyopathy including infarction Cardiac - arrhythmias (including changes in conduction) Cardiac - change in rate

REFERENCE :

BMJOAE British Medical Journal. (British Medical Assoc., BMA House, Tavistock Sq., London WC1H 9JR, UK) V.1- 1857- Volume(issue)/page/year: 304,1415,1992

TYPE OF TEST :

TDLo - Lowest published toxic dose

ROUTE OF EXPOSURE :

Oral

SPECIES OBSERVED :

Human - woman

DOSE/DURATION :

2 mg/kg/2D-I

TOXIC EFFECTS :

Behavioral - hallucinations, distorted perceptions Behavioral - excitement Behavioral - aggression

REFERENCE :

LANCAO Lancet. (7 Adam St., London WC2N 6AD, UK) V.1- 1823- Volume(issue)/page/year: 339,488,1992

TYPE OF TEST :

TDLo - Lowest published toxic dose

ROUTE OF EXPOSURE :

Intravenous

SPECIES OBSERVED :

Human - woman

DOSE/DURATION :

4 ug/kg

TOXIC EFFECTS :

Behavioral - convulsions or effect on seizure threshold Cardiac - EKG changes not diagnostic of specified effects Cardiac - pulse rate increase, without fall in BP

REFERENCE :

PECAE5 Pediatric Emergency Care. (Williams & Wilkins, 428 E. Preston St., Baltimore, MD 21202) V.1- 1985- Volume(issue)/page/year: 11,186,1995

TYPE OF TEST :

LD50 - Lethal dose, 50 percent kill

ROUTE OF EXPOSURE :

Oral

SPECIES OBSERVED :

Rodent - rat

DOSE/DURATION :

4200 mg/kg

TOXIC EFFECTS :

Behavioral - somnolence (general depressed activity) Behavioral - tremor Behavioral - rigidity (including catalepsy)

REFERENCE :

JTCEEM Journal de Toxicologie Clinique et Experimentale. (SPPIF, B.P.22, F-41353 Vineuil, France) V.5- 1985- Volume(issue)/page/year: 7,223,1987

TYPE OF TEST :

LD50 - Lethal dose, 50 percent kill

ROUTE OF EXPOSURE :

Intraperitoneal

SPECIES OBSERVED :

Rodent - rat

DOSE/DURATION :

1360 mg/kg

TOXIC EFFECTS :

Details of toxic effects not reported other than lethal dose value

REFERENCE :

DRFUD4 Drugs of the Future. (J.R. Prous, S.A., Apartado de Correos 540, 08080 Barcelona, Spain) V.1- 1975/76- Volume(issue)/page/year: 7,402,1982

TYPE OF TEST :

LD50 - Lethal dose, 50 percent kill

ROUTE OF EXPOSURE :

Intravenous

SPECIES OBSERVED :

Rodent - rat

DOSE/DURATION :

85 mg/kg

TOXIC EFFECTS :

Behavioral - convulsions or effect on seizure threshold Behavioral - rigidity (including catalepsy)

REFERENCE :

JTCEEM Journal de Toxicologie Clinique et Experimentale. (SPPIF, B.P.22, F-41353 Vineuil, France) V.5- 1985- Volume(issue)/page/year: 7,223,1987

TYPE OF TEST :

LD50 - Lethal dose, 50 percent kill

ROUTE OF EXPOSURE :

Oral

SPECIES OBSERVED :

Rodent - mouse

DOSE/DURATION :

1300 mg/kg

TOXIC EFFECTS :

Behavioral - somnolence (general depressed activity) Behavioral - tremor Behavioral - rigidity (including catalepsy)

REFERENCE :

JTCEEM Journal de Toxicologie Clinique et Experimentale. (SPPIF, B.P.22, F-41353 Vineuil, France) V.5- 1985- Volume(issue)/page/year: 7,223,1987

TYPE OF TEST :

LD50 - Lethal dose, 50 percent kill

ROUTE OF EXPOSURE :

Intraperitoneal

SPECIES OBSERVED :

Rodent - mouse

DOSE/DURATION :

4 gm/kg

TOXIC EFFECTS :

Details of toxic effects not reported other than lethal dose value

REFERENCE :

DRFUD4 Drugs of the Future. (J.R. Prous, S.A., Apartado de Correos 540, 08080 Barcelona, Spain) V.1- 1975/76- Volume(issue)/page/year: 7,402,1982

TYPE OF TEST :

LDLo - Lowest published lethal dose

ROUTE OF EXPOSURE :

Subcutaneous

SPECIES OBSERVED :

Rodent - mouse

DOSE/DURATION :

>1 gm/kg

TOXIC EFFECTS :

Details of toxic effects not reported other than lethal dose value

REFERENCE :

IYKEDH Iyakuhin Kenkyu. Study of Medical Supplies. (Nippon Koteisho Kyokai, 12-15, 2-chome, Shibuya, Shibuya-ku, Tokyo 150, Japan) V.1- 1970- Volume(issue)/page/year: 23,201,1992

TYPE OF TEST :

LD50 - Lethal dose, 50 percent kill

ROUTE OF EXPOSURE :

Intravenous

SPECIES OBSERVED :

Rodent - mouse

DOSE/DURATION :

143 mg/kg

TOXIC EFFECTS :

Behavioral - convulsions or effect on seizure threshold Behavioral - rigidity (including catalepsy)

REFERENCE :

JTCEEM Journal de Toxicologie Clinique et Experimentale. (SPPIF, B.P.22, F-41353 Vineuil, France) V.5- 1985- Volume(issue)/page/year: 7,223,1987

TYPE OF TEST :

LDLo - Lowest published lethal dose

ROUTE OF EXPOSURE :

Oral

SPECIES OBSERVED :

Mammal - dog

DOSE/DURATION :

>640 mg/kg

TOXIC EFFECTS :

Details of toxic effects not reported other than lethal dose value

REFERENCE :

IYKEDH Iyakuhin Kenkyu. Study of Medical Supplies. (Nippon Koteisho Kyokai, 12-15, 2-chome, Shibuya, Shibuya-ku, Tokyo 150, Japan) V.1- 1970- Volume(issue)/page/year: 23,201,1992

TYPE OF TEST :

LDLo - Lowest published lethal dose

ROUTE OF EXPOSURE :

Intravenous

SPECIES OBSERVED :

Mammal - dog

DOSE/DURATION :

>30 mg/kg

TOXIC EFFECTS :

Details of toxic effects not reported other than lethal dose value

REFERENCE :

IYKEDH Iyakuhin Kenkyu. Study of Medical Supplies. (Nippon Koteisho Kyokai, 12-15, 2-chome, Shibuya, Shibuya-ku, Tokyo 150, Japan) V.1- 1970- Volume(issue)/page/year: 23,201,1992

TYPE OF TEST :

LD50 - Lethal dose, 50 percent kill

ROUTE OF EXPOSURE :

Oral

SPECIES OBSERVED :

Rodent - rabbit

DOSE/DURATION :

2 gm/kg

TOXIC EFFECTS :

Behavioral - somnolence (general depressed activity) Behavioral - tremor Behavioral - rigidity (including catalepsy)

REFERENCE :

JTCEEM Journal de Toxicologie Clinique et Experimentale. (SPPIF, B.P.22, F-41353 Vineuil, France) V.5- 1985- Volume(issue)/page/year: 7,223,1987 ** REPRODUCTIVE DATA **

TYPE OF TEST :

TDLo - Lowest published toxic dose

ROUTE OF EXPOSURE :

Subcutaneous

DOSE :

21 mg/kg

SEX/DURATION :

female 14-20 day(s) after conception

TOXIC EFFECTS :

Reproductive - Effects on Newborn - behavioral

REFERENCE :

PNPPD7 Progress in Neuro-Psychopharmacology and Biological Psychiatry. (Pergamon Press Inc., Maxwell House, Fairview Park, Elmsford, NY 10523) V.6- 1982- Volume(issue)/page/year: 17,151,1993

TYPE OF TEST :

TDLo - Lowest published toxic dose

ROUTE OF EXPOSURE :

Subcutaneous

DOSE :

220 mg/kg

SEX/DURATION :

female 11-21 day(s) after conception

TOXIC EFFECTS :

Reproductive - Effects on Newborn - behavioral

REFERENCE :

GEPHDP General Pharmacology. (Pergamon Press Inc., Maxwell House, Fairview Park, Elmsford, NY 10523) V.6- 1975- Volume(issue)/page/year: 22,43,1991