Alfentanil - chemical structure
By Harbin / Public domain
![alfentanil chemical structure](alfentanil.png)
Buprenorphine - chemical structure
By Harbin / Public domain
![buprenorphine chemical structure](buprenorphine.png)
Codeine - chemical structure
By NEUROtiker / Public domain
![codeine chemical structure](codeine.png)
Fentanyl - chemical structure
By Harbin / Public domain
![fentanyl chemical structure](fentanyl.png)
Heroin - chemical structure
By NEUROtiker / Public domain
![heroin diacetylmorphine chemical structure](heroin.png)
Hydrocodone - chemical structure
By Yikrazuul / Public domain
![hydrocodone chemical structure](hydrocodone.png)
Hydromorphone - chemical structure
By Yikrazuul / Public domain
![hydromorphone chemical structure](hydromorphone.png)
Meperidine - chemical structure
By Ben Mills / Public domain
![meperidine chemical structure](meperidine.png)
Methadone - chemical structure
By Calvero / Public domain
![methadone chemical structure](methadone.png)
Morphine - chemical structure
By NEUROtiker / Public domain
![morphine chemical structure](morphine.png)
Tramadol - chemical structure
By Harbin / Public domain
![tramadol chemical structure](tramadol.png)