Current Scheduling Status
None
Year(s) and type of review / ECDD meetings
Drug Class
Recommendation (from TRS)
Substance identification
Metharbital (INN, CAS-50-11-3), chemically 5,5-diethyl-1-methylbarbituric acid, is also known as endiemal and metharbitone. The substance is a racemic mixture.
Similarity to known substances and effects on the CNS
Metharbital has been classified pharmacologically as an anticonvulsant barbiturate with a profile similar to that of phenobarbital. As it is an anticonvulsant barbiturate, it is presumed
that dose-related drowsiness, vertigo, confusion and incoordination can occur. The drug, like other barbiturates, is metabolized by hepatic microsomal enzymes and stimulates the production of these enzymes. Metharbital is metabolized to barbital which is controlled in Schedule IV of the Conventioonn Psychotropic Substances. The drug produces typical barbiturate-like anticonvulsant sedative-hypnotic effects on the central nervous system. As it is a hypnotic, it is presumed that tolerance, both natural and functional,
can occur. Cross-tolerance may occur to other barbiturates, ethanol, and other sedative-hypnotic drugs.
Dependence potential
Metharbital produces physical dependence of the barbiturate type, but there is no evidence on the ability of metharbital to induce psychic dependence in either animals or man in controlled laboratory studies.
Actual abuse and or/evidence of likelihood of abuse
There have been isolated reports on the abuse of metharbital from Norway and the United States of America. It is under national contro] in six countries. There have been sporadic reports of illicit trafficking and seizures of metharbital in the United States of America but not of clandestine manufacture. There were no reports of any public health and social problems caused by this substance.
Therapeutic usefulness
Metharbital is used as an anticonvulsant for the control ofepilepsy. It has also been reported to be effective for infantile myoclonic spasm. The drug is marketed only in New Zealand and
the United States of America, and only small amounts of the drug are used. The Committee rated the therapeutic usefulness for the treatment of epilepsy and infantile myoclonic spasm as high.
Recommendation
The Committee found that there was insufficient evidence that metharbital is being, or is likely to be, abused so as to constitute a public health and social problem warranting the placing of the substance under international control. On the basis of the limited data available concerning its pharmacological profile and on the fact that it induces physical dependence and that there are very limited reports of actual abuse, the Committee rated the likelihood of abuse of metharbital as moderate. The degree of the public health and social problems associated with the drug was found to be low and its therapeutic usefulness high. In the light of this assessment, the Committee recommended against scheduling of the drug.
Metharbital (INN, CAS-50-11-3), chemically 5,5-diethyl-1-methylbarbituric acid, is also known as endiemal and metharbitone. The substance is a racemic mixture.
Similarity to known substances and effects on the CNS
Metharbital has been classified pharmacologically as an anticonvulsant barbiturate with a profile similar to that of phenobarbital. As it is an anticonvulsant barbiturate, it is presumed
that dose-related drowsiness, vertigo, confusion and incoordination can occur. The drug, like other barbiturates, is metabolized by hepatic microsomal enzymes and stimulates the production of these enzymes. Metharbital is metabolized to barbital which is controlled in Schedule IV of the Conventioonn Psychotropic Substances. The drug produces typical barbiturate-like anticonvulsant sedative-hypnotic effects on the central nervous system. As it is a hypnotic, it is presumed that tolerance, both natural and functional,
can occur. Cross-tolerance may occur to other barbiturates, ethanol, and other sedative-hypnotic drugs.
Dependence potential
Metharbital produces physical dependence of the barbiturate type, but there is no evidence on the ability of metharbital to induce psychic dependence in either animals or man in controlled laboratory studies.
Actual abuse and or/evidence of likelihood of abuse
There have been isolated reports on the abuse of metharbital from Norway and the United States of America. It is under national contro] in six countries. There have been sporadic reports of illicit trafficking and seizures of metharbital in the United States of America but not of clandestine manufacture. There were no reports of any public health and social problems caused by this substance.
Therapeutic usefulness
Metharbital is used as an anticonvulsant for the control ofepilepsy. It has also been reported to be effective for infantile myoclonic spasm. The drug is marketed only in New Zealand and
the United States of America, and only small amounts of the drug are used. The Committee rated the therapeutic usefulness for the treatment of epilepsy and infantile myoclonic spasm as high.
Recommendation
The Committee found that there was insufficient evidence that metharbital is being, or is likely to be, abused so as to constitute a public health and social problem warranting the placing of the substance under international control. On the basis of the limited data available concerning its pharmacological profile and on the fact that it induces physical dependence and that there are very limited reports of actual abuse, the Committee rated the likelihood of abuse of metharbital as moderate. The degree of the public health and social problems associated with the drug was found to be low and its therapeutic usefulness high. In the light of this assessment, the Committee recommended against scheduling of the drug.
ECDD Recommendation
Scheduling/control not currently recommended
Link to full TRS
who_trs_741.pdf2.21 MB