Avoid potentially-interfering foods for several days prior to the test, particularly if both serum and urine catecholamines are to be measured. Consult your health care provider should be consulted regarding the need to discontinue potentially interfering drugs. Drugs that can decrease catecholamine measurements include clonidine, disulfiram, guanethidine, imipramine, MAO inhibitors, phenothiazines, salicylates, and reserpine. When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing .
Catecholamines are chemically-similar small molecules that are derived from the amino acid tyrosine.
Norepinephrine is the primary neurotransmitter in the sympathetic nervous system and is also in the brain. Epinephrine is a neurotransmitter in the brain but is also a major hormone in the body. Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.