Both Bontril and Adipex are appetite suppressant drugs; Bontril is the brand name for phendimetrazine while Adipex is the brand name for phentermine, according to Drugs.com. Adipex is manufactured by Teva Pharmaceuticals; Bontril is manufactured by Valeant Pharmaceuticals International.
Drugs.com states that the dosage for Adipex is usually 18.75 mg to 37.5 mg taken once per day before breakfast. The dosage for Bontril is a slow release capsule of 105 mg taken before breakfast or two to three immediate release doses of 35 mg before meals.
Both medications must be prescribed by a doctor and may interact with other medications. According to Drugs.com, Adipex may interact with many antidepressants. Bontril may interact with insulin, oral diabetes medications and some blood pressure medications. Neither medication should be taken with other diet pills.
Neither medication is safe for pregnant or nursing women, states Drugs.com. Adipex can pass into breast milk and negatively affect a nursing baby. It is unknown whether Bontril passes into breast milk.
Adipex is a schedule IV controlled substance, while Bontril is a schedule III controlled substance, according to Daily Med. The Drug Enforcement Administration states that schedule III controlled substances such as Bontril have a low to moderate risk of dependence, while schedule IV drugs, including Adipex have a low risk of dependence. Most individuals develop a tolerance to the effects of both medications within a few weeks, states Daily Med. When tolerance is reached, the drug should be discontinued.