Key takeaways

  • PDE5 inhibitors must not be combined with nitrates. SingHealth names glyceryl trinitrate, isosorbide mononitrate and isosorbide dinitrate, including medicines kept for occasional chest pain. SingHealth
  • Sildenafil, tadalafil, vardenafil and avanafil differ in timing, food effects, interactions and suitability. SingHealth describes delayed sildenafil onset after a high-fat meal and separate daily and when-needed tadalafil regimens. These are not strength rankings. SingHealth
  • Hidden ingredients are not limited to ED medicines. HSA’s February 2012 alert described four hospital admissions with very low blood sugar and glibenclamide detected in blood and urine; the products were suspected illegal sexual enhancers. HSA

ED pills and heart medicines: check nitrates before comparing

ED Pills and Heart Medicines: Check Nitrates Before Comparing

Before comparing sildenafil, tadalafil or another PDE5 inhibitor, check for nitrates and other chest-pain medicines. Combining a PDE5 inhibitor with a nitrate can cause a dangerous fall in blood pressure. Product duration, brand, price or a “natural enhancement” claim must never come before that interaction check.

Why is the nitrate interaction dangerous?

The combined blood-vessel effects can lower pressure dangerously. PDE5 inhibitors increase signalling that relaxes vessels; nitrates lower vascular tone too. Profound hypotension can cause dizziness, collapse, heart complications or inadequate blood flow to vital organs. HSA’s 2015 alert reported overseas deaths in patients using sildenafil while taking nitrates. HSA

Look for glyceryl trinitrate, isosorbide mononitrate or isosorbide dinitrate on the medicine list. SingHealth’s warning applies to both long-term and as-needed nitrate use. Short-acting sprays or tablets kept for an angina attack count, as do longer-acting isosorbide medicines. Include nicorandil and the other cardiovascular medicines for review of their own interaction details. SingHealth

Chest pain after an ED medicine needs emergency medical help. SingHealth specifically says not to use a nitrate for it. Tell responders the ingredient, product and time taken, including any sexual-enhancement supplement. Keep the packet or medicine-list entry available. Do not self-administer a nitrate unless the emergency team confirms the plan knowing about the PDE5 inhibitor exposure. SingHealth

How do sildenafil and tadalafil differ?

Tadalafil has a longer time course; that does not make it stronger than sildenafil. SingHealth describes when-needed sildenafil taken half an hour to an hour, or up to 4 hours, before sexual activity. Its when-needed tadalafil instructions allow at least half an hour and up to 36 hours beforehand. These intervals explain the timing difference; the prescription, conditions, interactions and adverse effects determine suitability. SingHealth

Daily tadalafil is a separate regimen, taken at around the same time each day regardless of sexual activity. SingHealth says the when-needed regimen uses a higher prescribed amount and should not be repeated continuously each day. Read which regimen was prescribed. A high-fat meal can delay sildenafil’s onset; tadalafil may be taken with or without food. These differences concern use, not a ranking of strength.

Vardenafil and avanafil add further differences. Food can affect some products more than others. Kidney or liver impairment may change exposure. Some combinations sold for sexual concerns contain another active medicine and should not be compared as if they were a higher-strength version of one ingredient.

The medicines facilitate an erectile response to sexual stimulation; they do not automatically address low desire, relationship concerns, pain, hormonal disorders or the cardiovascular and metabolic conditions that can contribute to erectile dysfunction. Persistent symptoms can be a reason for broader medical assessment rather than product escalation.

Which other medicines and conditions matter?

Other blood-pressure medicines, metabolic interactions and cardiovascular stability all need review. Alpha blockers and other blood-pressure medicines can add to dizziness or hypotension in some users. Strong inhibitors or inducers of drug-metabolising enzymes can change PDE5-inhibitor exposure. The complete medicine list should include HIV medicines, antifungals, antibiotics, prostate medicines, recreational substances and supplements. SingHealth also asks whether sildenafil or tadalafil is already being taken for another medical condition. That treatment needs to be visible before anyone considers an ED prescription. SingHealth

Heart disease does not create one universal answer. The cardiovascular safety of sexual activity and ED treatment depends on stability, symptoms and functional status. Recent heart attack or stroke, unstable angina, severe hypotension and certain uncontrolled cardiovascular conditions require clinician assessment.

Sudden vision or hearing change needs urgent attention. Tell the prescriber about previous eye or hearing problems too. An erection lasting four hours or more is an emergency because delay can damage tissue. SingHealth also lists seizures as a reason to stop and seek help immediately.

Headache can occur with either sildenafil or tadalafil. SingHealth describes sildenafil-related flushing as heat in the face or upper body; visual disturbance may include a blue tinge or blurred vision. Stomach upset, acid reflux, back pain, muscle ache and a blocked nose are more common with tadalafil. These symptoms should be discussed if concerning; sudden sensory loss belongs in the urgent group above. SingHealth

Why are “natural” enhancement products risky?

HSA testing has found potent undeclared medicines in products claiming to contain only herbs. Its 21 April 2015 alert named FORTA PLUS for Men as containing nortadalafil, a compound related to tadalafil, and STARKRx PERFORMANCE ENHANCER as containing sildenafil. Both had claimed natural herbal ingredients. HSA has also found undeclared tadalafil in illegal products. Unknown amounts, variable contents and poor manufacturing controls make the label unreliable for an interaction check. HSA alert

In the alert dated 6 February 2012, four men aged 30 to 78 had been admitted with dangerously low blood sugar. Two arrived unconscious. Three had no diabetes; the fourth had diabetes but was not prescribed glibenclamide. Tests found that medicine in their blood and urine. The patients could not identify the products positively, so HSA described illegal sexual-enhancement products as the likely cause based on the histories, tests and surveillance. HSA case report

Glibenclamide lowers blood glucose. HSA warned that severe hypoglycaemia can cause confusion, seizures and unconsciousness, progressing to coma or death without treatment. Claims of instant effects, extreme strength or no side effects do not establish safety. Products from messaging apps, informal marketplaces and unverifiable sellers can conceal an ingredient that makes a person unwell without their realising they took a medicine.

Do not combine two ED products or add an unverified supplement to “boost” a prescribed medicine. More ingredients can increase adverse effects without solving the reason for inadequate response.

What changes the answer?

Nitrates, cardiovascular stability, other medicines and the cause of the symptoms determine the assessment.

  • Nitrates and chest-pain treatment. Any current or emergency nitrate makes the interaction check decisive.
  • Cardiovascular stability. Recent events, uncontrolled symptoms and blood pressure require individual assessment.
  • Kidney and liver function. These can affect exposure and product suitability.
  • Other medicines. Alpha blockers and strong metabolic interactions may change the plan.
  • Timing and food. Product-specific onset, duration and food effects are practical differences, not potency rankings.
  • Cause of symptoms. Diabetes, vascular disease, medicine effects, hormones and psychological factors may need assessment.

Call emergency services for chest pain, collapse, severe breathlessness, stroke-like symptoms, sudden vision or hearing loss, or an erection lasting four hours or more. Tell responders about any ED medicine or supplement and when you used it. The erectile-dysfunction catalogue identifies ingredients for the medicine review; selection follows the nitrate and cardiovascular checks.

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