As the cliché goes, the best teacher of a doctor is the patient. There is nothing more true about it, especially on side effects of a drug.
Years ago, I had the opportunity of seeing a very pleasant 30-something male patient. He had been diagnosed with pheo by another doctor and saw me for a second opinion. He had been on phenoxybenzamine for the alleged specific anti-pheo effects for more than a year. His blood pressure was well controlled by phenoxybenzamine. After reviewing the numerous tests and imaging studies, I determined that he did not have pheo. I recommended using a diuretic medication for blood pressure control, instead of using the expensive phenoxybenzamine. He was so relieved once he learned that he would not absolutely need phenoxybenzamine—but not due to financial reasons. He told me that he could not have children while on the drug but his wife and he so much wanted to start a family. An inquisitive soul, I asked him to elaborate. The patient shyly told me that he had not had ejaculates after he was on phenoxybenzamine.
That was the first time I learned this very common side effect of phenoxybenzamine in men. We all know the standard common side effects such as nasal stuffiness, orthostatic hypotension, and fatigue. Ejaculatory failure happens in almost every man taking phenoxybenzamine. Most men do not complain of this side effect, probably because the treatment is usually short-term and patients have anxiety before operation so that they do not attempt sexual activity. Men may also be embarrassed to talk about this what is perceived by some as a sensitive but trivial symptom.
The mechanism of ejaculatory failure is not retrograde ejaculation, rather, patients simply do not transfer seminal fluid (the bulk of ejaculates) to be ejaculated. The good news is that this sexual side effect is completely reversible in 1-2 days after discontinuing phenoxybenzamine. And phenoxybenzamine does NOT affect libido, potency, or orgasm.
Prazosin and doxazosin usually do not cause ejaculatory problems but sometimes they do.
After I learned this side effect from that patient, I always inform my male patients of this unique side effect of phenoxybenzamine. Most of them appreciate my warning. Some would say “Doc, sex is the last thing I am thinking of now.” Hey, you never know. Sexual activity is generally not contraindicated in patients with pheo, provided that it is not particularly violent.
Dr. Pheo
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Dr. Pheo,
ReplyDeleteCould you lend some insight into why pheo researchers and clinicians seem to not be agressively exploring TKIs and other inhibitors as treatment for pheos and paragangliomas. I know there are some exploring this avenue of treatment, but it is not getting the same attention that one sees in treating patients with MTC. Is part of the issue that pheos tend to be labeled benign, and not have METs... therefore a surgical option is more curative? And is it that pheos can be caused by RET, SDHx, and VHL mutation so therefore there are more targets to consider and also with VHL the mutation actual results in a loss of function instead of gain?
Dear DJPheo,
ReplyDeleteThe difference between pheo and MTC is that most pheos are solitary (non-metastatic) while MTC is often already metastatic at diagnosis. Therefore for most patients with pheo, surgical resection is curative and the best option.
For metastatic pheo, the growth speed and symptoms are heterogeneous. The toxicities of TKIs are significant and should be weighed against the symptoms of metastatic pheo.
For molecular pathogenesis, the current understanding is that RET (MEN2) and NF1 (NF1) probably cause pheo through activating tyrosine kinases, while SDH and VHL by promoting angiogenesis (that's why avastin is used).
Hope I have at least answered some of your questions.
Dr. Pheo
Dr. Pheo,
ReplyDeleteI was recently diagnosed with extra-adrenal paraganglioma and told I have three tumors, bilateral cartotid with lymph node involvement and one in my trachea. I have a paralyzed vocal chord and the imaging studies showed that the tumor in my trachea is the cause. In addition I was diagnosed with PTC and had a total thyroidectomy. I was told the PGL are inoperable so I will have to do radiation therapy to stop their growth. The doctors that diagnosed this were ENT's at a large university hospital and I was referred to an Endocrinologist for follow up for the thyroid cancer. Perhaps my problem comes from having this diagnosed by the ENT. Wouldn't a full scan normally be done when PGL has already been diagnosed and are multiple. I ask this because my endo (also located at the same university) did not order further test or seem concerned about the PGL. I ended up back in his office last week because I have been having full blown "episodes", hbp, palpitations, tremors etc. He said he thinks I might have a pheo and wanted me to do the 24 hour urine test. Am I wrong to think that this is making me start back at square one?
Dear gtghawaii,
ReplyDeleteYour suspicion is correct. Although most neck paragangliomas do not secrete catecholamines, they occasionally do so. Therefore catecholamines or metanephrines should be checked in every patient with neck paraganglioma. You also need to do FDG-PET or MIBG scan NOW to see if you have paraganglioma/pheo in other parts of the body, which is especially important as you have bilateral tumors and metastasis.
Let me know if you have other questions.
Dr. Pheo
Dr. Pheo,
ReplyDeletePer your response above, am I to understand that there is no support for using Sutent for a patient with SDHB-caused metastatic disease?
Let me know.
Dear Denis,
ReplyDeleteAs far as I know, Sutent can be very effective against paraganglioma with SDHB mutations.
Dr. Pheo
In our experience phenoxybenzamine prevents ejaculation and thus makes sex painful. Doxasozin enables sex but didn't control adrenal production & increased the "impending sense of doom" which doesn't make you feel sexy anyway!
ReplyDeleteDear Jane,
ReplyDeleteThank you for sharing.
Dr. Pheo