Clinicians have tried for decades to help patients lose weight with the aid of medication.
Prior to the introduction of orlistat and sibutramine, the drugs available to aid weight loss were bulk-forming agents, such as methyl-cellulose, and centrally acting anorectics, such as phentermine.
Bulk-forming agents are rarely used now, quite simply because they don't work. Initial hopes that they could help patients decrease their dietary intake by creating a feeling of fullness have not been realized in clinical studies or in clinical experience.
Centrally acting anti-obesity drugs generally act in the brain to increase the release of serotonin and noradrenaline, resulting in decreased appetite. They act either on the serotonin pathways or on the catecholaminergic pathways. The most commonly used anorectic agent of recent years has been phentermine.
The centrally acting anorectics are virtually unused within the NHS, their last few remaining outlets being predominantly through private slimming clinics. The anorectic agents fenfluoramine and dexfenfluoramine fell out of use in 1997 after being withdrawn by the manufacturers. Phentermine and amfepramone have been serially licensed, withdrawn, reinstated, withdrawn and reinstated yet again. Currently, the manufacturers of phentermine and amfepramone are still engaged in legal disputes with the European regulatory authority, the CPMP, and their ultimate status is currently undecided.