Tadalafil is a widely prescribed phosphodiesterase type 5 (PDE5) inhibitor used to treat erectile dysfunction, benign prostatic hyperplasia, and pulmonary arterial hypertension in the UK. Whilst generally well tolerated, some patients wonder whether tadalafil can cause heart palpitations. Understanding the cardiovascular effects of this medication is essential for safe use. This article examines the relationship between tadalafil and palpitations, explains why cardiovascular symptoms may occur, and provides guidance on when to seek medical advice. We also outline important safety precautions and contraindications to help patients and clinicians make informed decisions about treatment.

What Is Tadalafil and How Does It Work?

Tadalafil is a prescription medicine licensed in the UK for treating erectile dysfunction (ED), benign prostatic hyperplasia (BPH), and pulmonary arterial hypertension (under separate marketing authorisation). It belongs to a class of drugs called phosphodiesterase type 5 (PDE5) inhibitors, which also includes sildenafil and vardenafil. Tadalafil is available under brand names such as Cialis and as generic formulations.

The mechanism of action centres on inhibiting the enzyme phosphodiesterase type 5, which is present in the corpus cavernosum of the penis and widely distributed in vascular smooth muscle, including the prostate and bladder. By inhibiting PDE5, tadalafil increases levels of cyclic guanosine monophosphate (cGMP), a chemical messenger that promotes smooth muscle relaxation and vasodilation. This enhanced blood flow facilitates penile erection in response to sexual stimulation and can also relieve urinary symptoms associated with BPH.

Tadalafil is notable for its long duration of action—up to 36 hours—which distinguishes it from shorter-acting PDE5 inhibitors. This extended half-life allows for greater spontaneity in sexual activity and once-daily dosing options. Licensed dosing regimens include:

• ED (on-demand): 10 mg (range 5-20 mg) taken before sexual activity

• ED (once-daily): 2.5-5 mg taken daily

• BPH: 5 mg once daily

The Medicines and Healthcare products Regulatory Agency (MHRA) regulates tadalafil in the UK, and it is available only on prescription following appropriate clinical assessment.

While tadalafil is generally well tolerated, understanding its pharmacological effects on the cardiovascular system is essential for both patients and prescribers, particularly given its vasodilatory properties and potential interactions with other medications.

Why Might Tadalafil Affect Your Heart Rate?

Cardiovascular effects of tadalafil arise primarily from its vasodilatory action. By inhibiting PDE5, tadalafil causes relaxation of vascular smooth muscle, leading to small mean reductions in blood pressure in healthy adults. These reductions are typically modest and well tolerated in most individuals, but larger drops can occur with concurrent use of nitrates, alpha-blockers or alcohol.

When blood pressure falls, the body's autonomic nervous system may respond by increasing heart rate to maintain adequate cardiac output and tissue perfusion. This reflex tachycardia could potentially be perceived as palpitations—an awareness of one's heartbeat that may feel rapid, forceful, or irregular. However, it is important to note that palpitations are not commonly reported with tadalafil use.

According to the Summary of Product Characteristics (SmPC) for tadalafil, palpitations are classified as an uncommon adverse effect (occurring in fewer than 1 in 100 patients). More frequently reported adverse effects include:

• Headache (common: may affect up to 1 in 10 people)

• Flushing (common: facial redness due to vasodilation)

• Dizziness (uncommon: may affect up to 1 in 100 people)

• Nasal congestion (common)

Patients with pre-existing cardiovascular conditions—such as coronary artery disease, heart failure, or arrhythmias—may be more susceptible to cardiovascular symptoms. Additionally, the concurrent use of nitrates or alpha-blockers can potentiate hypotensive effects, potentially increasing the likelihood of reflex tachycardia and palpitations. Therefore, careful patient selection and medication review are essential components of safe prescribing.

When to Seek Medical Advice About Palpitations

While occasional awareness of one's heartbeat is common and often benign, certain features warrant prompt medical evaluation. Patients taking tadalafil should be advised to:

Call 999 or attend A&E immediately if experiencing:

• Chest pain or tightness, particularly if radiating to the arm, jaw, or back

• Severe shortness of breath or difficulty breathing

• Fainting (syncope) or severe dizziness

Contact your GP urgently if you experience:

• Persistent or severe palpitations lasting more than a few minutes

• Irregular heartbeat or a sensation of skipped beats

• Sudden onset of palpitations accompanied by sweating, nausea, or anxiety

These symptoms may indicate underlying cardiac arrhythmias, myocardial ischaemia, or other serious cardiovascular events requiring assessment. Patients with known heart disease should be particularly vigilant, as tadalafil is not recommended in certain cardiac conditions.

For non-urgent concerns—such as occasional, brief palpitations without associated symptoms—patients should still discuss these with their GP at the next available appointment. The clinician can review the patient's medication history, assess cardiovascular risk factors, and determine whether further investigation is needed. Initial investigations typically include a thorough clinical history, physical examination, 12-lead electrocardiogram (ECG), and relevant blood tests (such as full blood count, kidney function, and thyroid function).

Patients should be encouraged to keep a symptom diary noting the timing, duration, and triggers of palpitations, as well as any concurrent medications or lifestyle factors (such as caffeine or alcohol intake). This information aids clinical assessment and helps differentiate benign palpitations from those requiring intervention. If you develop concerning symptoms, do not take further doses of tadalafil and seek medical advice promptly.

Safe Use of Tadalafil: Precautions and Contraindications

Safe prescribing of tadalafil requires careful patient assessment and adherence to established contraindications. The MHRA and NICE provide clear guidance on when tadalafil should not be used and which patients require additional monitoring.

Contraindications include:

• Concurrent use of nitrates (e.g., glyceryl trinitrate, isosorbide mononitrate) or nitric oxide donors, due to the risk of severe, potentially life-threatening hypotension (do not use nitrates within at least 48 hours of tadalafil)

• Concomitant use of guanylate cyclase stimulators such as riociguat

• Recent myocardial infarction (within 90 days), unstable angina, or stroke (within 6 months)

• Severe heart failure (NYHA Class III or IV)

• Uncontrolled hypertension or significant hypotension (<90/50 mmHg)

• Known hypersensitivity to tadalafil or any excipients

Warnings and precautions apply to patients with:

• Anatomical penile deformities (e.g., Peyronie's disease, angulation)

• Conditions predisposing to priapism (sickle cell anaemia, multiple myeloma, leukaemia)

• Bleeding disorders or active peptic ulceration

• Hereditary degenerative retinal disorders, including retinitis pigmentosa

• Hepatic impairment (daily dosing not recommended in severe impairment; caution with on-demand use)

• Severe renal impairment (dose adjustment necessary)

Important safety warnings:

• Priapism: Seek urgent medical care for erections lasting more than 4 hours

• Sudden vision or hearing loss: Stop taking tadalafil and seek immediate medical attention

Drug interactions are clinically significant. Alpha-blockers can cause additive hypotensive effects; patients should be stable on alpha-blocker therapy before initiating tadalafil at the lowest dose. Co-administration for BPH is generally not recommended. CYP3A4 inhibitors (such as ketoconazole, ritonavir, clarithromycin) increase tadalafil plasma concentrations, necessitating dose reduction. CYP3A4 inducers (e.g., rifampicin) may reduce tadalafil efficacy.

Patients should be counselled on lifestyle factors that may exacerbate cardiovascular symptoms, including excessive alcohol consumption, which can potentiate hypotensive effects. Regular medication reviews and cardiovascular risk assessments ensure ongoing safety.

Suspected adverse reactions should be reported via the MHRA Yellow Card Scheme (yellowcard.mhra.gov.uk).

Frequently Asked Questions