A compound represented by the formula (I) [R
1
to R
8
represent an alkyl group, an alkenyl group, and the like; n represents 0 or 1; R
4
represents an amino group or —(CX
2
)
m
—COOH (m represents 0 to 3, and X represents hydrogen atom); R
5
represents —(CY
2
)
p
—COOR
6
(p represents an 0 to 3, Y represents hydrogen atom, and R
6
represents hydrogen atom or an alkyl group)], or a salt thereof.
Silicon-Containing GABA Derivatives, Silagaba Compounds, as Orally Effective Agents for Treating Neuropathic Pain without Central-Nervous-System-Related Side Effects
Neuropathic pain is a chronic condition resulting from neuronal damage. Pregabalin, the (S)-isomer of 3-isobutyl-gamma-aminobutyric acid (GABA), is widely used to treat neuropathic pain, despite the occurrence of central nervous system (CNS)-related side effects such as dizziness and somnolence. Here we describe the pharmacology of novel GABA derivatives containing silicon-carbon bonds, silagaba compounds. Silagaba131, 132, and 161 showed pregabalin-like analgesic activities in animal models of neuropathic pain, but in contrast to pregabalin they did not impair neuromuscular coordination in rotarod tests. Pharmacokinetic studies showed that brain exposure to silagaba compounds was lower than that to pregabalin. Surprisingly, despite their potent analgesic action in vivo, silagaba compounds showed only weak binding to alpha 2-delta protein. These compounds may be useful to study mechanisms of neuropathic pain. Our results also indicate that silagaba132 and 161 are candidates for orally effective treatment of neuropathic pain without CNS-related side effects.