No one can purchase phentermine without a prescription, because it is a schedule IV controlled substance, says Drugs.com. Schedule IV controlled substances have an approved medical use in the United States but also a potential for abuse, explains Drugs.com. Purchasing any controlled substances without a prescription is illegal.
Phentermine causes difficulty sleeping, dry mouth, irritability, nausea and dizziness. A user also experiences raised blood pressure and serious effects such as uncontrolled muscle movements; a change in sexual interest; irregular, pounding or fast heartbeat; and mental or mood changes such as uncontrolled anger, nervousness and hallucinations. If a user experiences severe headache, weakness on one side of the body, blurred vision, a seizure or slurred speech, he should stop using the medication and seek medical attention immediately, cautions WebMD. Phentermine also causes heart or lung problems in rare conditions.
Patients use phentermine together with a doctor-approved diet and exercise program to lose weight. It is an appetite suppressor and is thought to work by either decreasing someone’s appetite, affecting certain parts of the brain or increasing the amount of energy used by the body, according to WebMD.
A patient should not take phentermine if he has hyperthyroidism, a history of drug abuse, glaucoma, a known hypersensitivity to sympathomimetic amines or a history of cardiovascular diseases such as stroke, arrhythmias or coronary artery disease, warns Drugs.com. Nursing or expectant mothers should also avoid phentermine. If a patient develops tolerance to the appetite suppressant effects of phentermine, he should discontinue its use rather than exceed the recommended dosage.