<unk>  is a semi-synthetic opioid analgesic prescribed for pain or severe dyspnea, or as an antitussive, either alone or compounded with paracetamol (as in co-dydramol) or aspirin. It was developed in Germany in 1908 and first marketed in 1911.
Commonly available as tablets, solutions, elixirs, and other oral forms,<unk>  is also available in some countries as an injectable solution for deep subcutaneous and intra-muscular administration. As with codeine, intravenous administration should be avoided, as it could result in anaphylaxis and dangerous pulmonary edema. In past times,<unk>  suppositories were used; however,<unk>  is available in suppository form on prescription.<unk>  is used as an alternative or adjunct to codeine for the aforementioned indications.  It is available as the following salts, in rough descending order of frequency of use:  bitartrate, phosphate, hydrochloride, tartrate, hydroiodide, methyliodide, hydrobromide, sulfate, and thiocyanate.  The salt to free base conversion factors are 0.67 for the bitartrate, 0.73 for the phosphate, and 0.89 for the hydrochloride.<unk>  was developed during the intense international search for more effective antitussives, especially to help reduce the airborne spread of tuberculosis, pertussis, pneumonia, and similar diseases, in the years from c.a. 1895 to 1915, and is similar in chemical structure to codeine. Depending on individual metabolism,<unk>  is 100 to 150 percent as strong as codeine[citation needed].  Although<unk>  does have extremely active metabolites, in the form of dihydromorphine and dihydromorphine-6-glucuronide (one hundred times more potent), these metabolites are produced in such small amount that they do not have clinically important effects.<unk>  is also the original member and chemical base of a number of similar semi-synthetic opiates such as acetyldihydrocodeine,<unk>  enol acetate, dihydroisocodeine, nicocodeine, and nicodicodeine.
Dihydrocodeine
Codeine
Norcodeine
Morphine 
Nalorphine
Oxycodone
Morpholine
Methadone 