Which side effect of phentermine may affect sleep patterns?

Phentermine is a central nervous system stimulant commonly used for weight management. One of its notable side effects is insomnia, which directly impacts sleep patterns. This occurs because phentermine increases neurotransmitter activity in the brain, particularly those involving norepinephrine and dopamine, leading to heightened alertness and reduced ability to fall or stay asleep.

Patients taking phentermine often report difficulty in achieving restful sleep, as the stimulating effects can linger past the time of administration, especially if taken later in the day. This significant side effect can interfere not only with sleep duration but also with sleep quality, ultimately affecting overall health and weight management efforts.

While phentermine may cause other side effects like constipation, xerostomia, and tachycardia, none of these directly influence sleep patterns to the same degree as insomnia does. Thus, insomnia is the most relevant concern when considering the impact of phentermine on sleep.