Double-blind, randomized, placebo-controlled clinical trials with non-prescription medications for the treatment of obesity

Objective: Phenylpropanolamine (PPA) and benzocaine are non-prescription me dications approved for treating obesity. The dose of PPA for weight loss is 75 mg/day. PPA has the same chemical similarity to pseudoephedrine that am phetamine has to methamphetamine. Because benzocaine causes weight loss by altering taste and PPA by central appetite suppression, they may induce add itional weight loss when combined. These studies explore the safety and eff icacy of low-dose PPA, pseudoephedrine, and PPA with benzocaine in causing weight loss. Research Methods and Procedures: Study 1 compared PPA 12.5 mg tid with 25 mg tid and placebo in a 6-week trial in 108 obese subjects. Study 2 compared pseudoep hedrine 120 mg/day and a placebo in a 12-week trial with 72 obese subjects. Study 3 compared 4 groups of 20 obese subjects using PFA 75 mg/day, benzoc aine gum 96 mg/day, PPA with benzocaine gum, and a placebo over 12 weeks. Results: Both doses of PPA gave twice the weight loss of placebo, but the d ifference did not reach statistical significance. Pseudoephedrine was no di fferent than placebo in inducing weight loss. The PPA with benzocaine group had more adverse events than the benzocaine group (p = 0.03), the placebo group (p = 0.03), or the PPA group (p = 0.09) without additional weight los s. Discussion: We conclude that further studies with low-dose PPA for weight l oss are indicated, that pseudoephedrine is not effective for weight loss, a nd that adding benzocaine to phenylpropanolamine increases adverse effects without increasing weight loss.