The rule of thumb I used was that if I was taking verapamil, I would limit myself to using an energy drink once a day. It was Carl D. that pointed me to a study showing that combining taurine and verapamil can cause some electrical problems with heartbeat regulation.

Anecdotally, I noticed a few times where my heart would seem to flutter a little or skip a beat if I had taken a 2nd or 3rd energy drink while on verapamil therapy. 

Taurine is a critical amino acid for the brain as it helps generate nerve impulses. It is crucial to newborns, since they cannot make it. Taurine functions in the brain and the heart to help stabilize cell membranes. It is also an antioxidant with detoxifying activities seen especially in the eyes and the lungs. Its main uses include treatment of epilepsy and ADHD where it acts as a mild sedative. Other common conditions helped by Taurine include fluid retention and high blood pressure.

# Benefits and Uses of Taurine include Arrhythmias
# Asthma
# Antioxidant for the eyes
# Bloating
# Blood Clots
# Breathing constriction
# Congestive heart failure
# Cystic fibrosis
# Diabetes/glucose metabolism
# Epilepsy
# Fat digestion
# Heart strength & rhythm
# High blood pressure
# Immune weakness
# Liver and Kidney disease
# Lung ailments
# Macular Degeneration
# Ovarian Cancer
# Vision impairment

Are there any nutrients that help Taurine work more effectively?
Magnesium, zinc, and B-complex all increase the effectiveness of Taurine.

What are some food sources of Taurine?
Clams, shellfish, seafood, and meat are all sources of Taurine.

Are there any drug contraindications with Taurine?
Taurine will lower blood pressure in hypertensives, and their medication will need to be reduced.

Heart Disease and Blood Pressure
Almost everyone with high blood pressure has benefited from Taurine supplementation. It helps by encouraging the excretion of excess fluid, which takes pressure of the blood vessels. It dampens the sympathetic nervous system, and relieves arterial spasms that can cause blood pressure to rise.

Seizure Disorders
It has been shown that patients with epilepsy or brain irritability often stop having seizures when they take Taurine regularly.

Protecting Vision
Taurine provides eyes with antioxidant protection. A deficiency of Taurine damages the retinas in people and animals.

Stabilizing Blood Sugar
Taurine helps stabilize blood sugar in both TypeI and TypeII diabetes.

Immune Weakness
Taurine helps rebuild a suppressed immune system by protecting white blood cells from self-destruction as they battle-invading microbes.

Breathing & Lung Protection
Taurine protects the lungs from free radical damage. Studies suggest that taurine offers nearly complete protection from respiratory hazards such as ozone. Asthma attacks are diminished significantly when 500mg of taurine is taken as a lung aerosol.