Dihydrocodeine is an opioid analgesic used as an alternative or adjunct to codeine to treat moderate to severe pain, severe dyspnea, and cough. It is semi-synthetic, and was developed in Germany in 1908 during an international search to find a more effective antitussive agent to help reduce the spread of airborne infectious diseases such as tuburculosis. It was marketed in 1911. Dihydrocodeine is metabolized to dihydromorphine -- a highly active metabolite with a high affinity for mu opioid receptors. Dihydrocodeine is used for the treatment of moderate to severe pain, including post-operative and dental pain. It can also be used to treat chronic pain, breathlessness and coughing. In heroin addicts, dihydrocodeine has been used as a substitute drug, in doses up to 2500mg/day to treat addiction.

Phenmetrazine is an anti-obesity drug, which was discovered by Boehringer-Ingelheim in 1952 and approved by FDA under the name Preludin. Later on the drug was withdrawn from the market due to the reported cases of abuse. According to some studies, misuse of phenmetrazine turned many young addicts to crime. It is suggested that the drug exerts its effect by inhibiting the monoamine transport.

Metopon was developed as an analgesic opium derivative. This drug has a high affinity to the mu-opioid receptor and produces antinociception through this receptor. Metopon was available in Canada only in tablet form for oral administration; however, because of the drug addiction, the Drug Addiction Committee recommended its limited use.

Secobarbital sodium, a barbiturate, is FDA approved for the treatment of insomnia and for pre-anesthetic use. This drug binds at a distinct site associated with a Cl- ionopore at the GABAA receptor, increasing the duration of time for which the Cl- ionopore is open. The post-synaptic inhibitory effect of GABA in the thalamus is, therefore, prolonged. Adverse reactions are drowsiness, lethargy, hangover, paradoxical excitement in elderly patients, somnolence. Rifampin may decrease secobarbital levels by increasing metabolism.

AMOBARBITAL is a barbiturate derivative with hypnotic and sedative properties. In an in vitro study in rat thalamic slices amobarbital worked by activating GABAA receptors, which decreased input resistance, depressed burst and tonic firing, especially in ventrobasal and intralaminar neurons, while at the same time increasing burst duration and mean conductance at individual chloride channels; this increased both the amplitude and decay time of inhibitory postsynaptic currents. Adverse effects are mainly a consequence of dose-related CNS depression and the risk of dependence with continued use is high.

Bezitramide was developed as an orally long-acting analgesic compound and was marketed under the brand name Burgodin. The overdose of this drug caused death that is why it was withdrawn from the market.