Nobody knows for sure, but cymbalta increases the duration of serotonin and
norepinepherine in nerve
synapses, suppressing acetylcholine (a pain and
muscle stimulating messenger), and increasing the release of dopamine (a "well" feeling and relaxing neurotransmitter). Missing a dose of cymbalta can tip the balance back to increased acetylcholine release, resulting in restlessness, increased pain, and increased blood pressure.