Highly variable, dependent on individual
For Clinical Opioid Withdrawal Scale (COWS) >=8: 4mg, observe 45min, redose if COWS remains >=8. Then discharge home with 16 mg a day for 2 days if you are able to prescribe, other wise consider return to the ER on day 2 and 3 for a 16 mg dose per day.
For Clinical Opioid Withdrawal Scale (COWS) 0-7: Do not dose in the ER. If you can prescribe consider unobserved home induction instructions available on paper  and app .
If sublingual tablets/films unavailable then intravenous/intramuscular formulation (dose 0.3-0.9 mg every 6-12 hours) has been used for opioid withdrawal in the ED and hospitalized patients.

Suboxone initial induction dose: 2mg/0.5mg or 4mg/1mg, titrate up by 2-4mg q2h based on withdrawal symptoms up to 8mg/1mg
Buprenorphine
Methadone
Naltrexone
Morphine
Tramadol
Dexmedetomidine
Codeine
Midazolam