Does tadalafil cause hypotension? Tadalafil, a phosphodiesterase type 5 (PDE5) inhibitor used to treat erectile dysfunction and benign prostatic hyperplasia, can lower blood pressure due to its vasodilatory effects. Whilst generally well tolerated, tadalafil may cause hypotension, particularly in patients taking nitrates, alpha-blockers, or those with pre-existing cardiovascular conditions. Understanding the risk factors, recognising symptoms, and adhering to prescribing guidance are essential for safe use. This article examines how tadalafil affects blood pressure, identifies at-risk groups, and outlines precautions to minimise hypotensive complications in line with UK clinical guidance.

What Is Tadalafil and How Does It Work?

Tadalafil is a prescription medicine 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 enzyme phosphodiesterase type 5, which is found in the smooth muscle of blood vessels, particularly in the corpus cavernosum of the penis and the pulmonary vasculature. During sexual stimulation, nitric oxide is released in the erectile tissue, activating an enzyme called guanylate cyclase. This increases levels of cyclic guanosine monophosphate (cGMP), which relaxes smooth muscle and allows increased blood flow into the penis, facilitating an erection. Tadalafil works by inhibiting PDE5, the enzyme responsible for breaking down cGMP. By preventing this breakdown, tadalafil prolongs the vasodilatory effects of nitric oxide, thereby enhancing erectile function.

Importantly, tadalafil does not cause erections without sexual stimulation—it simply enhances the natural erectile response. Beyond ED, tadalafil is also licensed for daily use at 5 mg to manage urinary symptoms associated with BPH, and at 40 mg once daily (as two 20 mg tablets of Adcirca or generic equivalent) for pulmonary arterial hypertension. For ED, tadalafil can be used either on-demand (10-20 mg) or as a daily 2.5-5 mg dose. Because tadalafil causes systemic vasodilation—relaxation of blood vessels throughout the body—it has the potential to lower blood pressure. This pharmacological effect underpins both its therapeutic benefits and its cardiovascular side effects, including the risk of hypotension.

Risk Factors for Low Blood Pressure with Tadalafil

While tadalafil is generally well tolerated, certain patient groups and clinical scenarios carry an increased risk of hypotension. Understanding these risk factors is essential for safe prescribing and patient counselling.

Concurrent use of nitrates is the most significant risk factor. Nitrates (such as glyceryl trinitrate, isosorbide mononitrate, or isosorbide dinitrate) are commonly prescribed for angina. Both nitrates and tadalafil increase cGMP levels, and their combined use can cause severe, potentially life-threatening hypotension. For this reason, tadalafil is absolutely contraindicated in patients taking any form of nitrate therapy, including short-acting sprays, tablets, and long-acting preparations. This contraindication also extends to recreational nitrates such as amyl nitrite ('poppers'). Importantly, nitrates must not be used within at least 48 hours after taking tadalafil due to its prolonged half-life.

Guanylate cyclase stimulators such as riociguat (used for pulmonary hypertension) are also contraindicated with tadalafil, as the combination can cause severe hypotension.

Alpha-blockers, used to treat hypertension or BPH, can also interact with tadalafil. Both drug classes cause vasodilation, and concurrent use may lead to additive blood pressure lowering. The risk varies between agents, with greater hypotension risk with doxazosin compared to tamsulosin. If co-prescription is necessary, tadalafil should be started at the lowest dose and only after the patient is stable on alpha-blocker therapy. For BPH, the combination of tadalafil with alpha-blockers is generally not recommended.

Other risk factors include:

• Pre-existing hypotension (resting systolic BP <90 mmHg)

• Severe cardiovascular disease, including recent myocardial infarction, stroke, or unstable angina

• Left ventricular outflow obstruction (e.g., aortic stenosis, hypertrophic cardiomyopathy)

• Autonomic dysfunction or conditions affecting blood pressure regulation

• Volume depletion or dehydration

• Concurrent antihypertensive therapy, particularly multiple agents

• Older age, where vascular responsiveness and compensatory mechanisms may be impaired

• Potent CYP3A4 inhibitors (e.g., ketoconazole, ritonavir) which can increase tadalafil exposure

Patients with these risk factors require careful assessment before tadalafil is prescribed, and in some cases, alternative treatments may be more appropriate.

Symptoms of Hypotension to Watch For

Hypotension—abnormally low blood pressure—can manifest with a range of symptoms, from mild and transient to severe and potentially dangerous. Patients prescribed tadalafil should be educated about the signs of low blood pressure and advised on when to seek medical attention.

Common symptoms of hypotension include:

• Dizziness or light-headedness, particularly on standing (orthostatic hypotension)

• Feeling faint or actually fainting (syncope)

• Blurred vision or visual disturbances

• Nausea

• Fatigue or unusual tiredness

• Poor concentration or confusion

• Palpitations (awareness of heartbeat)

These symptoms occur because reduced blood pressure compromises perfusion to vital organs, particularly the brain. Orthostatic hypotension—a drop in blood pressure upon standing—is particularly relevant with tadalafil, as vasodilation can impair the body's normal compensatory mechanisms.

In more severe cases, hypotension may lead to:

• Syncope (loss of consciousness), which carries a risk of injury from falls

• Chest pain or tightness, especially in patients with underlying coronary artery disease

• Shortness of breath

• Cold, clammy, or pale skin

• Rapid, shallow breathing

When to seek urgent medical help:

Patients should be advised to contact their GP or call NHS 111 if they experience persistent dizziness, recurrent light-headedness, or any concerning symptoms after taking tadalafil. They should call 999 or attend A&E immediately if they experience chest pain, severe breathlessness, loss of consciousness, or symptoms suggestive of a cardiovascular event.

If experiencing chest pain or other cardiac symptoms requiring emergency care, patients should inform healthcare staff that they have taken tadalafil within the past 48 hours, as this will affect treatment decisions (particularly regarding nitrate administration).

It is also important to counsel patients to avoid sudden postural changes—such as standing up quickly from sitting or lying—especially after taking tadalafil, and to sit or lie down if they feel faint. Alcohol can exacerbate hypotensive effects and should be consumed in moderation.

Safe Use of Tadalafil: Precautions and Contraindications

To minimise the risk of hypotension and other adverse effects, careful patient selection and adherence to prescribing guidance are essential. The MHRA and NICE provide clear recommendations for the safe use of tadalafil.

Absolute contraindications include:

• Concurrent nitrate therapy (in any form)

• Guanylate cyclase stimulators such as riociguat

• Recent cardiovascular events: myocardial infarction within the past 90 days, unstable angina, or stroke within the past 6 months

• Severe hypotension (resting systolic BP <90 mmHg) or uncontrolled hypertension

• Hypersensitivity to tadalafil or excipients

Special warnings and precautions:

• Severe hepatic impairment (Child-Pugh class C): tadalafil is not recommended

• Hereditary degenerative retinal disorders (e.g., retinitis pigmentosa): use with caution

• Previous episode of non-arteritic anterior ischaemic optic neuropathy (NAION): increased risk of recurrence; use with caution

• Alpha-blockers: caution with all agents, particularly doxazosin. For BPH, combination therapy is generally not recommended

• Potent CYP3A4 inhibitors (e.g., ketoconazole, ritonavir): may increase tadalafil exposure and hypotension risk

• Grapefruit juice: may increase tadalafil levels; avoid concurrent consumption

Dose adjustments:

• Renal impairment:
• For on-demand use: mild/moderate impairment—no adjustment; severe impairment—maximum 10 mg

• For once-daily use: mild impairment—no adjustment; moderate impairment—maximum 5 mg; severe impairment—not recommended

• Hepatic impairment: mild/moderate—maximum 10 mg for on-demand; severe—not recommended

• Elderly patients may be more susceptible to hypotensive effects; consider starting at lower doses

Patient counselling is critical and should include:

• Explanation of how tadalafil works and the importance of sexual stimulation

• Clear advice to never combine tadalafil with nitrates and to inform emergency staff about tadalafil use within the past 48 hours

• Guidance on recognising symptoms of hypotension

• Advice to avoid excessive alcohol, which can potentiate blood pressure lowering

• Information on common side effects: headache, flushing, dyspepsia, nasal congestion, and back pain

• Instructions to seek urgent medical attention for prolonged erection (priapism >4 hours) or sudden vision or hearing loss

Before prescribing tadalafil, a thorough cardiovascular assessment is recommended, particularly in men with risk factors for heart disease. UK clinical guidance recommends risk stratification to determine whether sexual activity—and therefore PDE5 inhibitor use—is safe for individual patients.

Patients should be encouraged to report suspected side effects via the MHRA Yellow Card scheme.

In summary, while tadalafil can cause hypotension due to its vasodilatory mechanism, careful patient selection, adherence to contraindications, appropriate dosing, and thorough patient education significantly reduce this risk, allowing safe and effective use for the majority of patients.

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