Can a psychiatric nurse practitioner prescribe medication?

Psychiatric nurse practitioners and clinical nurse specialists may be able to prescribe medications–this depends on the nurse practice act in the state in which they practice. Both are qualified to engage in psychotherapy. 

This may depend on the state in which the nurse works, but generally psychiatric nurse practitioners are legally allowed to prescribe drugs and often provide an alternative to psychiatrists (MDs who specialize in mental health) for the prescription and maintenance of medication for mental health disorders.

While psychiatric nurse practitioner training is very high level, it doesn't typically include depthful coursework in performing psychotherapy/talk therapy. However, there are many psychiatric nurse practitioners who seek out extra training so they can be qualified to perform talk therapy.

In an inpatient behavioral health facility, licensed psychiatric nurses (RNs with or without degrees) are trained and qualified to provide individual and group mental health therapy 24/7. The give medication as ordered by a physician.
Some also work in outpatient clinics and do the same thing.

Advanced practice master's level psychiatric nurses may be Clinical Nurse Specialists, Nurse Psychotherapists (like myself), or Nurse Practitioners. Depending on the state where they are licensed, they may or may not be able to prescribe medication. They are employed in a variety of settings–hospitals, clinics, and private/independent practice. They are qualified to provide individual, couple, family, and group therapy. They may use many modalities (depending on their education and training) like insight oriented, cognitive-behavioral, EMDR, hypnosis, solution focused therapy and art therapy.

All psychiatric nurses approach mental health therapy in a systematic and holistic manner. They "take into account" not only a person's emotional status, but also their physical well being, spiritual needs, and surrounding support.