Levomoramide is the levorotatory, biologically inactive isomer of dextromoramide.

Dextromoramide is a synthetic strong-acting opioid and full mu-opioid receptor agonist. Dextromoramide is a Schedule I drug illegal to possess. The current indication for Palfium® (dextromoramide) is severe acute or chronic pain requiring opioids, such as post-operative pain, and pain associated with bone fractures, malignancies and acute renal/biliary colic attacks in adults.

Ketobemidone (Cliradon, Ketogan, Ketodur, Cymidon) is a strong opioid analgesic, structurally related to pethidine, which has been in clinical use for more than 50 years. In the Scandinavian countries ketobemidone is only available in combination with a spasmolytic substance N,N-dimethyl-3,3-diphenyl-I-methylallylamine (A29). Ketobemidone has been shown to be a non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist. In spite of a relatively low mu-receptor affinity ketobemidone has a higher analgesic potency than morphine by systemic administration. It is probably due to its higher lipophilicity and consequently more easy penetration into the CNS. Ketobemidone is indicated for the treatment of all types of severe pain, such as postoperative, cancer, kidney stones and fractures.

Zipeprol is disubstituted piperazine that is marketed as a non-opioid antitussive in Europe, Asia, and South America. Zipeprol is not available in the United States or Canada and has been discontinued in Europe. Zipeprol is still available in some countries in Asia and South America. Zipeprol was demonstrated to have anticough effects in animal models, to be active as a blocker of histamine and cholinergic function, to be a potent local anesthetic and to possess bronchiospasmolytic actions. it had no remarkable cardiovascular or gastrointestinal actions in the rat or dog in comparison to codeine.

Piritramide is a synthetic opioid that has been used formore than 30 years in parts of Europe as the analgesic of choice for the management of postoperative pain. Piritramide was discovered at Janssen Pharmaceutica in 1960 and is currently manufactured and distributed within continental Europe and some other places by Janssen-Cilag. Piritramide is not available in all countries. It is marketed under the brand name Dipidolor in Germany, Lithuania, Slovenia, Austria. Piritramide is most commonly prescribed i.m. or i.v. for postoperative analgesia. It is used successfully for patient-controlled analgesia in adults 14 and more recently in chil-dren. Piritramide has potency 0.65 to 0.75 times that of morphine. Upon administration, piritramide binds to and activates mu-opioid receptors in the central nervous system (CNS), thereby mimicking the effects of endogenous opioids and producing analgesic relief. The most common side effect of piritramide appears tobe a dose-related incidence of sedation. It is reported in many studies, but rarely accurately quantified. Diaphoresis, urinary retention, flushing, focal myopathy and thrombophlebitis have all been reported. Piritramide is a strong opioid and therefore is regulated much the same as morphine in all known jurisdictions. It was never introduced in the United States and is therefore a Schedule I/Narcotic controlled substance. It is listed under international treaties and other laws such as the German Betabungsmittelgesetz, the Austrian Suchtgiftmittelgesetz, the Opium Laws of various other European countries, Canadian controlled substances act, UK Misuse of Drugs Act of 1971, and equivalents elsewhere.

TILIDINE is a low to medium potency opioid analgesic. It is metabolized to its active metabolites, nortilidine and bisnortilidine. Its analgesic activity is largely exerted through nortilidine which is a potent agonist at Mu opioid receptors.

Alphacetylmethadol (INN), aka α-acetylmethadol (AAM), is a synthetic opioid analgesic. Its levorotary enantiomer, levacetylmethadol, is an FDA-approved treatment for opioid addiction. Alphacetylmethadol is very similar in structure to methadone, a widely-prescribed treatment for opioid addiction. In the United States, it is a Schedule I controlled substance under the Controlled Substances Act with an ACSCN of 9603 and a 2013 annual manufacturing quota of 2 grams. Studies in rats indicate that alphacetylmethadol also evokes the heroin-like discriminative stimulus effects.

Allylprodine (Ro 2-7113) is an opioid analgesic. It is stereoselective, with one isomer being much more active. Allylprodine is included in Schedule I of the US Controlled Substances Act 1970 as a Narcotic with ACSCN 9602 and a 2014 annual aggregate manufacturing quota of 2 grammes.

Difenoxin is a 4-phenylpiperidine which is closely related to the opioid analgesic meperidine. Difenoxin alone is a USA Schedule I controlled drug, as it may be habit forming. However, it is listed as a Schedule IV controlled drug if combined with atropine, which is added to decrease deliberate misuse. Motofen(R) is a brand mixture which combines atropine sulfate and difenoxin hydrochloride. It is approved by the FDA to treat acute and chronic diarrhea. Difenoxin is an active metabolite of the anti-diarrheal drug, diphenoxylate, which is also used in combination with atropine in the brand mixture Lomotil(R). It works mostly in the periphery and activates opioid receptors in the intestine rather than the central nervous system (CNS). Difenoxin is also closely related to loperamide, but unlike loperamide it is still capable of crossing the blood brain barrier to produce weak sedative and analgesic effects. However, the antidiarrheal potency of difenoxin is much greater than its CNS effects, which makes it an attractive alternative to other opioids. Motofen(R) is a combination of atropine, an anticholinergic drug, and difenoxin, an antidiarrheal drug. It has been used in many countries for many years as a second line opioid-agonist antidiarrheal, which exists an intermediate between loperamide and paragoric. Diarrhea which is a result of cyclic or diarrhea predominant Inflammatory Bowel Syndrome may not be treated effectively with difenoxin, diphenoxylate, or loperamide. As such, diarrhea and cramping which does not respond to non-centrally acting derivatives or belladonna derivatives such as atropine are often treated with conservative doses of codeine. In patients with acute ulcerative colitis, as induction of toxic megacolon is possible, and thus use of Motofen(R) is cautioned. Motofen(R) has been assigned pregnancy category C by the FDA, and is to be used only when the potential benefits outweigh the potential risk to the fetus. The safety of use during lactation is unknown and thus not recommended. Each five-sided dye free MOTOFEN® tablet contains: 1 mg of difenoxin (equivalent to 1.09 mg of difenoxin hydrochloride) and 0.025 mg of atropine sulfate (equivalent to 0.01 mg of atropine). Difenoxin acts as an antidiarrheal by activating peripheral opioid receptors in the small intestine and thereby inhibiting peristalsis. However, research has suggested that non-opioid receptor pathways exist. This would explain the potent antidiarrheal effects of difenoxin despite only limited opioid action.