Those arrested include Mohamad Basir Alam (35), Riyajudin Ansari (20), Kalima Khatun (40), Jarina Khatun (35) and Islam Miya aka Munna from Motihari district of Bihar, police said.
They have confiscated 2800 ampules of Buprenorphin, 1,000 ampules of Buprenorphin and diazepam and 1,000 ampules of Buprenorphin during raids at various locations in the Nepalese capital.
Police have also arrested four Nepalese and seized 400 ampules of Buprenorphin and 3363 ampules of diazepam from them.
This is the largest haul of contraband drugs seized by the police in the recent time.
Further investigation into the matter is going on, they said.