Coughing After an Injection (POME) in Athletes: Causes and the Link with Pharmacology
A sudden urge to cough, tightness in the throat or chest and breathlessness within minutes of an intramuscular injection is frightening, and in gym circles it is often brushed off as "tren cough" or "oil cough". The medical name for the best-described version of this reaction is pulmonary oil microembolism, or POME. Our editorial team explains what is known about it, which medicines it is linked with, and why such episodes should never be dismissed.
What POME is
Pulmonary oil microembolism describes a reaction in which tiny droplets of an oil-based medicine enter the bloodstream during or shortly after an intramuscular injection and travel to the lungs. There they lodge in small blood vessels and provoke irritation and inflammation of the airways and lung tissue.
The result is a characteristic cluster of symptoms, most notably an urge to cough or a coughing fit, which typically begins during the injection or within minutes afterwards. Many episodes resolve on their own within minutes to an hour, but some are more severe and require medical treatment.
The mechanism is thought to involve the oily vehicle, such as castor oil, and the solvent benzyl benzoate rather than the hormone itself. The more viscous the formulation and the larger the injected volume, the greater the theoretical opportunity for small amounts to reach a blood vessel.
POME is well documented with medically prescribed long-acting testosterone undecanoate. The same physical principles can apply to other oil-based depot injections, which is why the condition is relevant to sports pharmacology more broadly.
Which medicines are involved
The clearest association is with long-acting injectable testosterone undecanoate, marketed in the UK as Nebido and in the United States as Aveed. Clinical trial and post-marketing data led regulators to include warnings about POME and anaphylaxis in the product information. In the US, Aveed carries a boxed warning and can only be given in certified healthcare settings with a 30-minute observation period afterwards.
Middleton and colleagues reviewed routine clinical use of testosterone undecanoate injections at an Australian andrology clinic and reported that POME-type reactions occurred in a small minority of injections, mostly mild and self-limiting. A post-marketing analysis by Pastuszak and colleagues similarly found such events to be uncommon but real.
| Feature | Medical setting | Non-medical setting |
|---|---|---|
| Product | Licensed, sterile, known composition | Often unknown composition, solvents and concentration |
| Administration | Trained professional, slow injection | Self-administered, variable technique |
| Observation | Monitoring after injection | Usually alone, no monitoring |
| Response to reaction | Immediate assessment and treatment | Delay, reluctance to seek help |
In the bodybuilding world, coughing after injection is commonly attributed to particular anabolic compounds. There is little formal research on these anecdotes. Underground products frequently contain high concentrations of solvents to keep large amounts of active substance in solution, and their exact composition is unknown, making it impossible to say with certainty which component is responsible.
This lack of data is itself a safety problem: users and the people around them may assume a known, harmless explanation when the true cause could be different and more serious.
Symptoms and similar conditions
Typical POME symptoms include an urge to cough, coughing fits, throat tightness, chest discomfort, shortness of breath, sweating and dizziness. Symptoms usually start during or within minutes of the injection.
The danger is that several more serious conditions can look similar at first. Doctors consider:
- Anaphylaxis — a severe allergic reaction with hives, swelling of the lips or tongue, wheeze, and a drop in blood pressure.
- Pulmonary embolism — a blood clot in the lungs, causing breathlessness, chest pain and sometimes coughing up blood. Risk is increased by raised haematocrit.
- Asthma attack or airway reaction to an excipient.
- Infection — if fever and cough develop hours or days later, possibly from a non-sterile product.
Because these conditions overlap, a person cannot reliably diagnose POME on their own. In the clinic, staff assess vital signs, oxygen levels and the overall picture before deciding whether further treatment or investigation is needed.
Risk factors and the problem of non-medical use
In clinical guidance, slow injection into a large muscle by trained staff is used to minimise the risk of POME with testosterone undecanoate, and patients are observed afterwards. These precautions exist precisely because the reaction cannot be entirely prevented.
Outside medical settings, the situation differs substantially. People injecting anabolic steroids usually do so alone, with products whose ingredients, concentration and sterility are unverified. The Endocrine Society statement by Pope and colleagues documents the wider range of harms associated with non-prescribed use, including infections, cardiovascular disease and endocrine disruption.
Supraphysiological doses of androgens can increase haematocrit, which raises the risk of blood clots. A person who has a "cough" after injection while their blood is thickened may in fact be experiencing a clot rather than oil microembolism. This possibility is one reason why self-diagnosis is risky.
Our editorial team does not provide injection techniques or advice on continuing non-prescribed use. The safest way to avoid these reactions is not to inject unprescribed substances, and anyone who does should be aware of confidential harm-reduction services and seek medical help without delay when symptoms occur.
What to do and when to call 999
Call 999 immediately if coughing is accompanied by difficulty breathing, wheeze, swelling of the face, lips or tongue, a widespread rash, chest pain, fainting, blue lips, or if symptoms are getting worse rather than better. These are signs of a potentially life-threatening reaction.
Also seek urgent care for coughing up blood, one-sided chest pain on breathing, or breathlessness that develops hours or days after the injection. These may indicate a blood clot or infection.
If you are receiving prescribed testosterone injections and have experienced a reaction, tell your clinician before the next dose. They may change the formulation or the way it is given, and will document the event. Reactions can also be reported to the MHRA through the Yellow Card scheme.
When seeking help, be honest about what was injected. Emergency staff are focused on treating you safely, and knowing the substance and its vehicle helps them do that.
Conclusions of the editorial team
POME is a recognised reaction to oil-based intramuscular injections, best documented with long-acting testosterone undecanoate. It typically causes coughing and breathlessness within minutes of injection.
Most episodes in clinical settings are mild and short-lived, but POME cannot be reliably distinguished from anaphylaxis or pulmonary embolism without medical assessment.
In non-medical use, unknown product composition and raised haematocrit add further risk. Worsening or severe symptoms always warrant a 999 call.
We also recommend our articles on haematocrit and blood thickness, injection-site infections, and the risks of underground pharmaceuticals.
References
- Middleton T, Turner L, Fennell C, et al. Complications of injectable testosterone undecanoate in routine clinical practice. Eur J Endocrinol. 2015;172(5):511–517.
- Pastuszak AW, Hu Y, Freid JD. Occurrence of pulmonary oil microembolism after testosterone undecanoate injection: a postmarketing safety analysis. Sex Med. 2020.
- Wang C, Harnett M, Dobs AS, Swerdloff RS. Pharmacokinetics and safety of long-acting testosterone undecanoate injections in hypogonadal men: an 84-week phase III clinical trial. J Androl. 2010;31(5):457–465.
- Pope HG Jr, Wood RI, Rogol A, et al. Adverse health consequences of performance-enhancing drugs: an Endocrine Society scientific statement. Endocr Rev. 2014;35(3):341–375.
- Bhasin S, Brito JP, Cunningham GR, et al. Testosterone therapy in men with hypogonadism: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2018;103(5):1715–1744.
