Clinicians are calling for patient information leaflets to be updated after a woman had a life-threatening allergic reaction to an antibiotic in her partner’s semen. They also want healthcare workers to be made aware of such risks during their medical training.
“If you read any drug leaflet, they list a whole bunch of super-rare risks, so it’s not unreasonable to also include this risk on those leaflets to boost awareness,” says Cassim Akhoon at King’s College Hospital in London.
The woman developed anaphylaxis, a serious allergic reaction, due to probable exposure to the antibiotic amoxicillin via her partner’s semen. He took the drug to treat a sinus infection 6 hours before they had penetrative vaginal sex without a condom.
The partner of the woman asked his doctor whether it was safe for the couple to have unprotected sex because she had a history of allergic reactions to penicillins, a group of antibiotics, of which amoxicillin is one of the most commonly prescribed. “He was explicitly reassured by his doctor that she would not be at risk of allergic reactions,” says Akhoon, who is part of a team that examined the case after the event.
But 5 minutes after ejaculation, the woman developed symptoms of anaphylaxis. “Everything started to swell. I couldn’t breathe,” she told . “Obviously, nearly dying is quite a terrifying experience.”
The woman self-administered an EpiPen, a device that injects a shot of the hormone adrenaline into the body to halt anaphylaxis. Paramedics then arrived and treated her with further adrenaline. She was taken to hospital and was discharged 6 hours later.
The healthcare workers who treated her seemed to be unaware that exposure to amoxicillin via semen is possible, the woman says, and some of them assumed she must have taken the drug. “I wasn’t taught about this in medical school,” says Akhoon. “I definitely think we should make this part of formal medical training.”
About a year after the incident, Akhoon and his colleagues confirmed the woman’s allergy to amoxicillin via a skin test. This has led them to conclude that exposure via semen was the most likely cause. Around 1 per cent of people have allergies to penicillins, as confirmed via skin-prick tests, but anaphylaxis as a result of exposure to these drugs is extremely rare.
Antibiotics enter the bloodstream and can then reach the prostate and the seminal vesicles, a pair of pouch-like glands situated behind the bladder, which produce most of the fluid that makes up semen, says Akhoon. Prior studies have also found that amoxicillin is excreted in urine, suggesting it can persist in the urethra – a thin tube that transports urine and semen – until it is flushed out during ejaculation, he says.
Earlier case reports have described similar incidences, with one woman developing anaphylaxis after exposure to amoxicillin during oral sex. The team thinks the evidence that such transmission routes are a risk is strong enough to list it on the patient information leaflets provided alongside medications.
Amoxicillin’s leaflet already lists a rare side effect called aseptic meningitis, says Akhoon, which occurs when tissue around the brain and spinal cord become inflamed. “We don’t have any mechanistic proof that amoxicillin was absolutely, definitely the cause [of related meningitis cases], yet because of [the] high likelihood of causality, it’s mentioned on the leaflet.”
There isn’t sufficient evidence to list a risk of transmission via semen for other antibiotics or drugs, but this may emerge in future case reports, says Ahkoon. “As people consider this route of transmission more, we might start to get a bigger collection of cases to determine which drug classes are implicated.” There is also no evidence that transfer of antibiotics via vaginal fluid could lead to allergic reactions in sexual partners, he says.
The team has submitted the findings to the UK’s Medicines and Healthcare Products Regulatory Agency, which will decide whether updates to amoxicillin leaflets are needed. It couldn’t respond to a request for comment before this article was published.
Once informed, “people can then wear condoms or avoid sex until the antibiotics course is over”, says Patrick Yong at Frimley Park Hospital in Surrey, UK, who also examined the case.
Consultant allergist Chris Rutkowski in London thinks the most effective way of avoiding such transmissions is for the risk to taught during medical training. “Not because it’s common, but because the cost of missing it is high,” he says.