Does tadalafil cause blood clots? This is a common concern among patients prescribed this medication for erectile dysfunction or benign prostatic hyperplasia. Tadalafil, a phosphodiesterase type 5 (PDE5) inhibitor available in the UK under brand names such as Cialis, works by dilating blood vessels to improve blood flow. There is no evidence that tadalafil increases the risk of venous thromboembolism (blood clots in veins). However, understanding its cardiovascular effects, contraindications, and when to seek medical advice is essential for safe use. This article examines the relationship between tadalafil and clotting risk, drawing on UK regulatory guidance and clinical evidence.

What Is Tadalafil and How Does It Work?

Tadalafil is a prescription medication primarily used to treat erectile dysfunction (ED) and benign prostatic hyperplasia (BPH). It belongs to a class of drugs called phosphodiesterase type 5 (PDE5) inhibitors, which also includes sildenafil and vardenafil. In the UK, tadalafil is available under brand names such as Cialis, as well as generic formulations approved by the Medicines and Healthcare products Regulatory Agency (MHRA).

The mechanism of action centres on the relaxation of smooth muscle tissue within blood vessels. Tadalafil works by inhibiting the PDE5 enzyme, which normally breaks down cyclic guanosine monophosphate (cGMP). By blocking this enzyme, tadalafil allows cGMP levels to rise, leading to vasodilation—the widening of blood vessels. In the context of erectile dysfunction, this increased blood flow to the penile tissues facilitates an erection in response to sexual stimulation. For BPH, the same vasodilatory effect helps relax smooth muscle in the prostate and bladder, improving urinary symptoms.

Tadalafil is typically prescribed for ED at doses of 10-20 mg taken as needed before sexual activity, or at lower doses of 2.5-5 mg once daily. For BPH, the standard dose is 5 mg once daily.

Tadalafil is also licensed for the treatment of pulmonary arterial hypertension (PAH) under the brand name Adcirca, where it reduces blood pressure in the lungs by dilating pulmonary arteries. PAH treatment is specialist-initiated and monitored. The drug has a relatively long half-life of approximately 17.5 hours, which distinguishes it from other PDE5 inhibitors and allows for once-daily dosing in some indications.

There is no evidence that tadalafil increases the risk of venous thromboembolism. Its primary pharmacological action is vasodilation, which affects blood flow. However, understanding the broader cardiovascular context and individual risk factors is essential when considering this medication.

Risk Factors and Cardiovascular Considerations with Tadalafil

UK SmPCs and NICE sources do not show an increased risk of venous thromboembolism (VTE) with tadalafil. Rare serious cardiovascular events (e.g., myocardial infarction, stroke) have been reported, usually in those with underlying cardiovascular disease, with uncertain causality.

Tadalafil is absolutely contraindicated with:

• Any nitrate medications (including recreational 'poppers' containing amyl nitrite)

• Riociguat (a guanylate cyclase stimulator used for pulmonary hypertension)

Tadalafil is generally not recommended in patients with:

• Recent myocardial infarction (within 90 days)

• Recent stroke (within 6 months)

• Unstable angina

• Heart failure (NYHA class II-IV) within the last 6 months

• Uncontrolled arrhythmias

• Hypotension (blood pressure below 90/50 mmHg)

• Uncontrolled hypertension

Risk factors for venous thromboembolism (VTE) include prolonged immobility, recent surgery, malignancy, obesity, smoking, and inherited clotting disorders. These factors are unrelated to tadalafil's mechanism of action but should be part of a comprehensive cardiovascular risk assessment.

Important drug interactions include:

• Nitrates – severe, potentially fatal hypotension (absolute contraindication)

• Alpha-blockers – caution due to additive blood pressure-lowering effects; combination for lower urinary tract symptoms is generally not recommended; if necessary for ED, ensure stability on alpha-blocker first and use lowest tadalafil dose

• Strong CYP3A4 inhibitors (e.g., ketoconazole, itraconazole, ritonavir) – may increase tadalafil exposure

• Strong CYP3A4 inducers (e.g., rifampicin) – may reduce tadalafil effectiveness

• Grapefruit juice – may increase tadalafil levels

• Other antihypertensives – additive blood pressure-lowering effects

Patients on anticoagulants (such as warfarin, apixaban, or rivaroxaban) can generally take tadalafil as no direct interaction is expected, but this should be under medical supervision.

NICE recommends that prescribers conduct a thorough cardiovascular assessment before initiating PDE5 inhibitors, ensuring that any treatment aligns with the patient's overall health status and concurrent medications.

Recognising Symptoms of Blood Clots While Taking Tadalafil

There is no evidence that tadalafil increases VTE risk; however, it's important to recognise symptoms promptly regardless of cause. Rare cardiovascular events have been reported post-marketing in people with underlying cardiovascular disease.

Blood clots can occur in veins (venous thromboembolism, including deep vein thrombosis and pulmonary embolism) or arteries (arterial thrombosis, such as stroke or myocardial infarction).

Symptoms of deep vein thrombosis (DVT) typically affect the legs and include:

• Swelling in one leg (rarely both)

• Pain or tenderness, often starting in the calf

• Warmth and redness over the affected area

• Heavy or aching sensation in the leg

If a clot dislodges and travels to the lungs, it causes a pulmonary embolism (PE), which is a medical emergency. Warning signs include:

• Sudden shortness of breath or difficulty breathing

• Sharp chest pain that may worsen with deep breathing or coughing

• Rapid heart rate or palpitations

• Coughing up blood

• Feeling faint or dizzy

Arterial clots present differently. Symptoms of a stroke include sudden weakness or numbness (especially on one side of the body), confusion, difficulty speaking, vision problems, severe headache, or loss of balance. Signs of a heart attack include central chest pain or discomfort (often described as pressure or tightness), pain radiating to the arm, jaw, or back, shortness of breath, nausea, and sweating.

Any patient experiencing these symptoms, whether taking tadalafil or not, should seek urgent medical attention. Prompt recognition and treatment of blood clots significantly improve outcomes and reduce the risk of serious complications.

When to Seek Medical Advice About Tadalafil and Clotting Concerns

Patients taking tadalafil should maintain open communication with their GP or prescribing clinician, particularly if they have concerns about cardiovascular health or clotting risks. Routine follow-up is advisable to monitor treatment efficacy, side effects, and any changes in overall health status.

Seek immediate medical attention (call 999 or attend A&E) if you experience:

• Symptoms suggestive of pulmonary embolism (sudden breathlessness, chest pain, coughing blood)

• Signs of stroke (sudden weakness, speech difficulties, facial drooping)

• Symptoms of heart attack (severe chest pain, arm or jaw pain, sweating)

Contact your GP or NHS 111 urgently for same-day assessment if you notice:

• Suspected DVT symptoms (leg swelling, pain, redness, warmth)

Contact your GP or healthcare provider promptly if you notice:

• Unexplained shortness of breath or reduced exercise tolerance

• Persistent chest discomfort or palpitations

• Any new symptoms that concern you while taking tadalafil

Before starting tadalafil, inform your doctor about:

• Personal or family history of blood clots or clotting disorders

• Cardiovascular conditions (heart disease, stroke, hypertension)

• Current medications, including anticoagulants, antiplatelets, nitrates, alpha-blockers, and strong CYP3A4 inhibitors/inducers

• Recent surgery or prolonged immobility

• Other risk factors such as smoking, obesity, or cancer

Important safety information:

• Never take tadalafil with nitrates (including recreational 'poppers') or riociguat as this can cause a dangerous drop in blood pressure

• Avoid grapefruit juice while taking tadalafil

• Always inform healthcare professionals about all medications you are taking

If you experience any suspected side effects from tadalafil, report them via the MHRA Yellow Card Scheme (yellowcard.mhra.gov.uk or the Yellow Card app).

NICE guidance supports shared decision-making between patients and clinicians, ensuring that treatment choices align with individual risk profiles and preferences. If you have ongoing concerns about tadalafil and cardiovascular health, request a medication review. Your GP can assess whether tadalafil remains appropriate or whether alternative treatments should be considered. Patient safety is paramount, and any uncertainty warrants professional evaluation rather than discontinuing medication without medical advice.

Frequently Asked Questions