Catecholamines – Adrenal Pharmacology

by Pravin Shukle, MD

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    00:01 The adrenal medulla is responsible for catecholamine production.

    00:05 Because we already covered this in the autonomic nervous sytem section of pharmacology, we won't discuss it here.

    00:16 There is one thing I want to mention however, with respect to the adrenal medulla.

    00:20 I want to talk about a cancer or a lesion called pheochromocytoma.

    00:26 Pheochromocytoma is a neuroendocrine tumour. It is often found in the adrenal gland but it can be found outside the adrenal gland as well.

    00:35 It results in excess production of catecholamines, mostly norepinephrine.

    00:40 We can do all kinds of tests. One of the most easy and simple test is the 24 hour metanephrine test of the urine.

    00:47 We check for vanillylmandelic acid and metanephrines as a routine in a 24 hour test, but we can also do clinical testing and take a look at patients' blood pressure and heart rate and see that they tend to have very high levels.

    01:02 Serum testing can also be done. It is exceedingly expensive, but it's highly accurate.

    01:07 I rarely have done serum testing on patients when I'm diagnosing pheochromocytoma we've actually made a diagnosis just with the 24 hour urine and clinically, and we've had actually managed to remove successfully many pheochromocytomas.

    01:23 Remember that plasma metanephrines can also be analyzed. We would be looking specifically for normetanephrine and metanephrine.

    01:32 Treatment of pheochromocytoma is invariably surgical. We have to remove the tumour.

    01:37 Now there are some pharmacological treatments that we do utilize. These are not permanent treatment therapies.

    01:43 These are just hold over treatment therapies or bridge therapies.

    01:46 Phenoxybenzamine, we've learnt about this drug in the CNS lectures, is a nonspecific irreversible alpha blocker.

    01:56 A short acting alpha blocker is prazosin. We can also use terazocin as well.

    02:03 Now, the other thing that we like to use is labetolol which has combined alpha and beta blocker activity to help us control the heart rate.

    02:11 It's important that we never use a specific beta 1 blocker, because when you give a beta 1 blocker to a patient with pheo, you're gonna have unopposed alpha activity. And for the purposes of the exams, we're going to always say never use a specific beta 1 blocker.

    02:30 In reality, sometimes we have, but I won't get into why, and I want you to forget what I just said.

    02:35 On your exam, never use a beta 1 blocker, remember that part.

    02:40 Now, in terms of volume repletion, remember that you want to give these patients fluids.

    02:45 And sometimes we actually do something called "salt loading" in some patients.

    02:49 That's a specific issue that we deal with in the pre-operative clinic.

    About the Lecture

    The lecture Catecholamines – Adrenal Pharmacology by Pravin Shukle, MD is from the course Endocrine Pharmacology.

    Included Quiz Questions

    1. 24-hour urine for VMA and metanephrines
    2. Full body CT
    3. Urine test for sugars
    4. 24-hour urine for normetaneprhine
    5. Blood test for VMA
    1. Surgery
    2. Alpha and beta blockers
    3. Alpha blockers only
    4. Beta blockers only
    5. Monitoring with 24-hour urine for VMA and metanephrines

    Author of lecture Catecholamines – Adrenal Pharmacology

     Pravin Shukle, MD

    Pravin Shukle, MD

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