4'-Chlorodiazepam (Ro5-4864)
4'-Chlorodiazepam (Ro5-4864) is a chlorinated diazepam analogue best known in research as a selective ligand of the translocator protein (TSPO, the peripheral benzodiazepine receptor) rather than a classical CNS benzodiazepine. Unlike diazepam it has weak activity at the central GABA-A benzodiazepine site and in animals can be convulsant rather than anticonvulsant.
01 Overview
Ro5-4864 is used mainly as a pharmacological tool to probe TSPO, a mitochondrial protein involved in steroidogenesis and cellular stress responses. Its profile differs sharply from ordinary benzodiazepines: it binds poorly to the central benzodiazepine site and has shown proconvulsant and anxiogenic effects in some animal models.
Human use data are essentially absent; it appears in the research-chemical market largely by association with the benzodiazepine family. Its distinct target and potential to lower seizure threshold make it poorly comparable to sedative benzodiazepines, and its safety in humans is uncharacterised.
02 Mechanism
Selective ligand of the 18 kDa translocator protein (TSPO / peripheral benzodiazepine receptor); weak affinity for the central GABA-A benzodiazepine site.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Threshold | 1–5 mg | Oral | No established human dosing; values are speculative and use is discouraged. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| TSPO modulationModulation of mitochondrial translocator protein, studied for steroidogenesis and neuroinflammation. | Preclinical | ||
| Weak sedationLimited central sedative activity relative to classical benzodiazepines. | Unconfirmed |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Proconvulsant activityIn animal studies Ro5-4864 can lower seizure threshold and produce convulsions, opposite to typical benzodiazepines. | Severe | Unknown in humans | Preclinical | |
| Respiratory depression in combinationAs with other CNS depressants, combined use with opioids or alcohol may suppress respiration. | Life-threatening | Unknown | Unconfirmed |