Natural derivatives (Opiates): Heroin, Morphine, Codeine, Hydrocodone, Oxycodone (+ UDS)
Synthetic: Fentanyl, Hydromorphone, Buprenorphine, Methadone, Meperidine, Dextromethorphan (- UDS)<unk>  can be precipitated with administration of antagonist (e.g. naloxone) or partial agonist (e.g. buprenorphine)  or as a result of cessation of use
Symptoms are usually uncomfortable but not life-threatening and manifest with agitation and restlessness but does not cause altered mental status
Symptoms may resemble those of Influenza 
Catecholamine surge during withdrawal may cause a level of hemodynamic instability that may not be tolerated by patients with co-morbid conditions
Withdrawal can be life-threatening in neonates
Catecholamine surge during withdrawal may cause a level of hemodynamic instability that may not be tolerated by patients with co-morbid conditions
Withdrawal can be life-threatening in neonates
Heroin: onset 6-12 hours, peak 24-72 hours, duration 7-10 days
Methadone: onset 24-72 hours, peak 4-6 days, duration 14 days or more
Fentanyl: onset 2-5 hours, peak 8-12 hours, duration 4-5 days
Buprenorphine: 4-48 hours, peak 96 hours, duration 14-21 days
Naloxone: onset 1-3 min, duration: 30-60min
Butorphanol or nalbuphine: 15 min, duration: 90 min
Naltrexone: 15-30min, duration 12-24hours
Buprenorphine: 10-15min, duration 12-24 hours
Heroin: onset within 24hrs
Methadone: onset within 2-3 days due to large volume of distribution
Buprenorphine: onset within 2-3 days
Opioid withdrawal
Differential is largely based on clinical symptoms and history
Benzodiazepine withdrawal
Sepsis
Cocaine withdrawal
Influenza
Alcohol withdrawal
Clonidine withdrawal