Does tadalafil increase uric acid levels? This is a question that concerns some men prescribed this medication for erectile dysfunction or benign prostatic hyperplasia. Tadalafil, a phosphodiesterase type 5 (PDE5) inhibitor available in the UK under brand names including Cialis, works by improving blood flow but does not directly affect purine metabolism or uric acid handling. Current medical evidence and regulatory guidance show no established link between tadalafil use and elevated uric acid. This article examines the available clinical data, explores tadalafil's metabolic effects, and clarifies when uric acid monitoring may be appropriate.

What Is Tadalafil and How Does It Work?

Tadalafil is a prescription medication primarily used to treat erectile dysfunction (ED) and the symptoms of 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 inhibition of the PDE5 enzyme, which is found in the smooth muscle cells lining blood vessels. Under normal circumstances, sexual stimulation triggers the release of nitric oxide in the penile tissue, which activates an enzyme called guanylate cyclase. This leads to increased levels of cyclic guanosine monophosphate (cGMP), a molecule that relaxes smooth muscle and allows blood vessels to dilate. PDE5 normally breaks down cGMP, but tadalafil blocks this process, thereby prolonging vasodilation and improving blood flow to the penis, facilitating an erection.

Tadalafil is also licensed for pulmonary arterial hypertension under the brand name Adcirca, where its vasodilatory effects help reduce blood pressure in the lungs. The drug has a notably long half-life of approximately 17.5 hours, which allows for once-daily dosing in some patients. Common doses for ED range from 10 mg to 20 mg taken as needed, or a lower daily dose of 2.5 mg to 5 mg. For BPH, a 5 mg daily dose is typically prescribed.

NICE Clinical Knowledge Summary guidance supports the use of PDE5 inhibitors as a first-line pharmacological treatment for erectile dysfunction after appropriate assessment and counselling.

Important safety information: Tadalafil is contraindicated with nitrates and riociguat due to potentially dangerous drops in blood pressure. Caution is also needed when taking alpha-blockers, as the combination may cause symptomatic hypotension in some patients.

Understanding Uric Acid and Its Role in the Body

Uric acid is a natural waste product formed from the breakdown of purines, which are compounds found in certain foods (such as red meat, seafood, and alcohol) and also produced by the body's own cells. Under normal physiological conditions, uric acid is dissolved in the blood, filtered by the kidneys, and excreted in urine. Maintaining appropriate uric acid levels is essential for metabolic health, as both elevated and very low levels can have clinical consequences.

Hyperuricaemia is generally defined as serum uric acid levels above 360 µmol/L in women and 420 µmol/L in men, although reference ranges may vary between laboratories. It's important to note that many people with hyperuricaemia remain asymptomatic, and elevated uric acid alone does not constitute a diagnosis of gout.

When hyperuricaemia leads to the formation of urate crystals in joints and soft tissues, it can cause gout—a painful inflammatory arthritis characterised by sudden, severe attacks of joint pain, swelling, and redness, most commonly affecting the big toe. According to NICE guidance (NG219), treatment targets for gout typically aim for serum urate below 360 µmol/L (or below 300 µmol/L in severe tophaceous disease). Chronic hyperuricaemia is also associated with kidney stones, chronic kidney disease, and has been linked to cardiovascular risk factors, although the causal relationship remains under investigation.

Several factors influence uric acid levels, including:

• Dietary intake of purine-rich foods

• Alcohol consumption, particularly beer and spirits

• Medications such as diuretics, low-dose aspirin, and certain immunosuppressants

• Metabolic conditions including obesity, insulin resistance, and metabolic syndrome

• Genetic factors affecting uric acid excretion

Routine monitoring of uric acid is not standard practice in the general population but may be indicated in patients with gout, recurrent kidney stones, or those on medications known to affect uric acid metabolism. Understanding these baseline factors is important when evaluating whether a new medication might influence uric acid levels.

Potential Side Effects of Tadalafil on Metabolic Health

When considering whether tadalafil increases uric acid levels, it is important to examine the available clinical evidence and the drug's known metabolic effects. There is no official link established between tadalafil use and elevated uric acid levels in the current medical literature or regulatory guidance. Hyperuricaemia is not listed as an adverse reaction in the UK Summary of Product Characteristics (SmPC) for tadalafil products. Tadalafil's primary pharmacological action is vascular, and it does not directly interfere with purine metabolism or renal uric acid handling.

The most commonly reported side effects of tadalafil relate to its vasodilatory properties and include:

• Headache (very common, affecting more than 1 in 10 people)

• Flushing and facial warmth

• Dyspepsia (indigestion)

• Nasal congestion

• Back pain and myalgia (muscle aches), which are common side effects though the exact mechanism remains unclear

• Dizziness, particularly when combined with antihypertensive medications

From a metabolic perspective, tadalafil does not significantly affect glucose metabolism, lipid profiles, or electrolyte balance in most patients. Some studies have explored potential cardiovascular benefits of PDE5 inhibitors beyond their primary indication, including effects on endothelial function and insulin sensitivity, but these remain areas of ongoing research rather than established clinical effects.

It is worth noting that lifestyle factors commonly associated with erectile dysfunction—such as obesity, metabolic syndrome, excessive alcohol intake, and certain dietary patterns—are themselves risk factors for hyperuricaemia. Therefore, any observed correlation between tadalafil use and elevated uric acid is more likely attributable to these underlying conditions rather than the medication itself.

Patients should seek immediate medical attention if they experience an erection lasting more than 4 hours (priapism), sudden vision or hearing loss, chest pain, or severe dizziness. Suspected side effects can be reported via the MHRA Yellow Card scheme.

When to Monitor Uric Acid Levels While Taking Tadalafil

For the vast majority of patients taking tadalafil, routine monitoring of uric acid levels is not necessary unless there are specific clinical indications unrelated to the medication itself. However, certain circumstances may warrant closer attention to metabolic parameters, including uric acid.

Patients should consider discussing uric acid monitoring with their GP if they:

• Have a personal or family history of gout or recurrent kidney stones

• Are taking other medications known to affect uric acid levels, such as thiazide diuretics, loop diuretics, or low-dose aspirin

• Have chronic kidney disease, where impaired renal function may affect uric acid excretion

• Experience new symptoms suggestive of gout, including sudden onset of severe joint pain, swelling, warmth, and redness

• Have multiple cardiovascular risk factors or metabolic syndrome, where comprehensive metabolic assessment may be appropriate

When to seek medical advice:

Patients taking tadalafil should contact their GP or NHS 111 if they develop:

• Sudden, severe joint pain, particularly in the big toe, ankle, or knee

• Unexplained swelling or redness in joints

• Symptoms of kidney stones, such as severe flank pain, blood in urine, or difficulty passing urine

• Any new or worsening side effects that concern them

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

• An erection that lasts more than 4 hours

• Sudden vision or hearing loss

• Chest pain, severe dizziness, or collapse

If uric acid monitoring is deemed appropriate, this typically involves a simple blood test measuring serum uric acid concentration. Management of elevated uric acid, if detected, would follow standard NICE guidance (NG219) for hyperuricaemia and gout, which may include dietary modification, lifestyle changes, and in some cases, urate-lowering therapy such as allopurinol. Tadalafil itself would not typically need to be discontinued based on uric acid levels alone, as there is no established causal relationship, though any medication changes should be made in consultation with a healthcare professional, considering the overall benefit-risk profile for the individual patient.

Frequently Asked Questions