[Question #2837] Syphilis - Follow Up

40 months ago
Hello again,

I posted last month regarding concern over a lesion I had developed below my lip which I was worried may have been a syphilis chancre. I still have nagging doubt over the presentation and was looking for a little more advice. On my last post I didn’t mention that 2 weeks before my EIA blood test I was given 1g of azithromycin by what I now consider an over various doctor when I went for my throat swabs. Since our conversation, I have since read this can be effective against syphilis. My main question is whether this could have produced a false negative result and in any way masked the infection in the test? My doctor has said that it wouldn’t impact the test at all but wanted to get your opinion too.  Thankyou again for your time.
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
40 months ago
Welcome back to the forum, but sorry to see you found it necessary. I scanned your previous discussion with Dr. Hook.

Azithromycin 1 g would abort or cure incubating syphilis, if you had acquired it. However, the drug does not "mask" infection or make tests falsely negative:  in this situation, it would prevents development of a positive test by curing the infection. In other words, your test result remains valid and proves you did not catch syphilis; or, less likely but theoretically possible, that you were infected but then cured. Either way, you do not have syphilis now.

Best wishes. Let me know if anything isn't clear.

HHH, MD

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40 months ago
Thank you very much for your response, that aligns with the information given to me by my GP.  Apologies for my lack of understanding of the interactions between antibiotics and antibodies, but would it have been feasible for the azithromycin to have delayed the production of antibodies meaning the test would have turned positive later? Or does this have no influence on their production. Thanks yet again! 
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
40 months ago
No, that scenario is not known to occur. If you had received an antibiotic with only partial efficacy, e.g. if you'd received a non-curative dose of azithromycin (under 500 mg, as a guess), there might be delayed antibody production. But not with 1 g, which is a fully effective dose even against long-established syphilis.

You seem to be obsessed with a sexual decision you regret. But don't confuse that reaction with infectious outcomes from that decision. Deal with the former as you need to (counseling, maybe?) but you can discount and disregard the latter.

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40 months ago
Many thanks for your response - I wasn’t aware that a 1g dosage of azithromycin was effective against syphilis. I was under the impression 2g was required?  This does a lot to reassure me.

A great deal of my anxiety is borne from the fear of passing it on to family members through pecks on the cheek / lips. Is this a possible route for transmission? Having said that, if I understand correctly the lesion I had could never have been a chancre as it appeared c.10 days after I took the antibiotics. Is this correct?

To your final point, I have started CBT in an attempt to get control of my anxiety around this incident.

As I said on my previous thread, the service and expertise provided here are incredibly valuable and amongst the myriad of conflicting information online it is a great relief to have a trusted resource to call upon when needed. Thank you all.
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
40 months ago
Although 2 g is recommended when syphilis is treated with azithromycin, this is intentional overkill; 1 g is generally believed to be effective.

Syphilis is not transmitted by the sort of casual contact you describe. For example, household and family members of people with syphilis never catch it themselves except for especially intminate contact, e.g. nursing babies (and of course sex partners).

Thanks for the thanks about our services.
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