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 catecholamines and metanephrines
    2. Adrenal CT scan
    3. Urine test for glucose
    4. Adrenal MRI
    1. Surgery
    2. Alpha and beta blockers
    3. Alpha blockers only
    4. Beta blockers only
    5. Ketoconazole

    Author of lecture Catecholamines – Adrenal Pharmacology

     Pravin Shukle, MD

    Pravin Shukle, MD

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