Physiology case study?

A 28-year-old man presented to the hospital complaining of uncontrollable twitching of his extremities. He had a long history of uncomplicated intranasal heroine use and denied intravenous (IV) drug use, other substance abuse, of medical or surgical problems. He noted that he had recently changed his supplier of heroine. On examination he was found to be well developed, well nourished, and obviously uncomfortable. His vital signs were: blood pressure: 138/84mm Hg; pulse, 110 beats/min, respiratory rate, 24breaths per minute, and rectal temperature, 99 degrees F (37.2 C). Physical examination was normal except for the neurological assessment. He was awake, alert, and fully oriented. His limbs showed irregular and bilateral spontaneous contractions, and their activity increased while he was examined. His mental status remained unchanged during these movements. Strength and sensation were within normal limits, and reflexes were brisk. Chovestk and Trousseau signs were negative.

The patient was attached toa cardiac monitor, and an IV line was inserted. Blood was sent for a complete blood count (CBC), serum electrolytes, glucose, calcium, magnesium, and creatine phosphokinase. A urinalysis was also requested. An electrocardiogram (ECG) showed a normal sinus rhythm with normal axis and intervals and a Motion artifact.

What is the different diagnosis of this patient's disorder? What are three possible physiological imbalances or toxins that could cause the above signs and/or symptoms?

Why is this probably not a seizure disorder?

What is the most likely diagnosis?

State the neurological mechanism behind the problem. (What neurotransmitter mechanism is at work here)?

How should the patient with this clinical presentation be evaluated (diagnostic test) and treated? What are two diagnostic tests that could be used?

What are two possible treatments for this problem?

Any help you could give me in figuring out what is wrong with this person would be greatly appreciated. Thank you in advance for your help!