Hydroxypethidine, an opioid analgesic is an opioid receptor agonist. Hydroxypethidine is under the control of narcotic drugs according to US Single Convention 1961.

Acetorphine is a synthetic narcotic analgesic. Acetorphine was reported to have uses in veterinary medicine with pronounced advantages in the immobilization of the giraffe in which toxic effects were reduced as compared to the effects of etorphine. In July 1966, the Director-General of the World Health Organization informed the Secretary-General that WHO had arrived at the conclusion that etorphine and acetorphine should be included in Schedule I of the Convention, since they could give rise to similar abuse, and produce similar ill effects as the substances already listed therein. Acetorphine is a Schedule I controlled substance in the United States.

Trimeperidine (promedol) is the earliest and mostly studied opioid analgesic. Trimeperidine stimulates opioid receptors in the central nervous system. Compared with morphine, it has a weaker and shorter analgesic effect, less affects the respiratory, vomiting and vagal centers, does not cause smooth muscle spasm (except for the myometrium), and has a moderate antispasmodic and hypnotic effect. It is used to treat severe pain syndrome, acute left ventricular failure, pulmonary edema, cardiogenic shock, preparation for surgery, childbirth, high fever, post-transfusion complications, poisoning with atropine, barbiturates, barium, gasoline, boric acid, strong acids, carbon monoxide, turpentine, formalin, formalin. It has several side effects. Administration of this substance is associated with the development of life-threatening conditions accompanied by the suppression of respiration center. Analgesic trimeperidine (promedol) was included into the health care kits by various Ministries of the Russian Federation at different times.

Alphameprodine (ACSCN 9604) is an opioid analgesic classified by the United States Drug Enforcement Administration under Schedule I of illegal substances. The stereoisomer betameprodine is similarly classified, however alphameprodine is more widely used (both are referred to as Meprodine). Alphameprodine is a structural analogue of meperidine. It exerts physiological effects characteristic of opioids, such as analgesia, euphoria and sedation, as well as itching, nausea, and respiratory depression.

Dimenoxadol is an opioid analgesic which produces typical opioid effects such as analgesia and sedation. It is structurally similar to methadone and is a benzilic acid derivative. In the United States it is classified as a Schedule I controlled drug.

Dimethylthiambutene is the synthetic narcotic analgesic agent. It has analgesic effect similar to those of meperidine. The (+)-enantiomer of dimethylthiambutene is more active than the (-)-isomer. Dimethylthiambutene clinically compared with meperidine (pethidine), but maintains the dependence-producing capability of morphine. It has had illicit use in Japan in the past. Dimethylthiambutene is under international control according to the UN Single Convention 1961 and its amendments, Schedule I.

Phenadoxone hydrochloride is one of some forty amino-ketones and amino-esters related to amidone. The compound is a very potent analgesic for the rat; by the subcutaneous route it is more active than either morphine or amidone. In spite of this its acute toxicity to mice is lower than that of amidone and its therapeutic index is therefore correspondingly higher, giving a wider margin of safety. Side effects in dogs, such as narcosis, sedation, and general depression, were much less with phenadoxone than with amidone or morphine. Nausea and vomiting did not occur after phenadoxone in non-tolerant dogs. Clinical results show that for relieving certain types of pain in human subjects it is a potent analgesic that compares favorably with morphine and amidone. At therapeutic dose levels undesirable pharmacological effects, such as cardiac depression and vasomotor disturbance, are absent, and it is only at extremely high dose levels that untoward effects occur. However, the drug has a strong respiratory depressant action when given in high doses; it should be used with special caution if injected intravenously.

Phenomorphan is the μ-opioid receptor agonist. Phenomorphan is a synthetic narcotic analgesic structurally related to racemorphan and racemethorphan. It has no accepted medicinal value in the United States.

Properidine is an isopropyl analog of pethidine that acts as opioid analgesic.

Phenampromide is an opioid analgesic, which is considered to be structurally similar to isomethadone. Phenampromide belongs to the ampromide family of drugs, which also include propiram and diampromide. According to the literature, (R)-phenampromide has greater analgesic potency than its (S)-enantiomer. Synthetic narcotic analgesic phenampromide is under international control according to the UN Single Convention 1961 and its amendments, Schedule I.