Erectile Dysfunction: The Doses, Why the Tablets Seem to Fail and What ED Says About Your Heart

An erection is a blood flow event. Which means that when erections become unreliable, the first question is not about confidence or age — it is about the arteries, and that question has a number attached to it.

🔍 Four systems, and which one is yours

An erection needs open arteries, working nerves, adequate testosterone and a nervous system that is not in alarm mode. The pattern of the problem usually says which layer is involved.

The simplest clue is free. Morning erections present means the plumbing and the nerves work, and the problem is more likely to be situational or anxiety-driven. Morning erections absent for weeks or months points at a physical cause and deserves investigating properly.

🧪 What should be checked

1. 🩸 Blood pressure, which is both a cause and a thing ED predicts
2. 🍬 HbA1c or fasting glucose. ED is a common first presentation of type 2 diabetes
3. 📉 Lipid profile
4. 🧬 Morning testosterone, fasting, on two separate days — particularly where desire is also reduced
5. 🧫 Thyroid function, full blood count, and kidney and liver function
6. 😴 A question about snoring and daytime sleepiness, since sleep apnea contributes through both testosterone and vascular routes
7. 🚬 An honest account of smoking, alcohol and weight, which are the three modifiable factors with the largest effect

❤️ Is it safe for the heart?

These drugs do not strain the heart in themselves — sexual activity does, modestly. The standard approach divides men into three groups.

• 🟢 Low risk — controlled blood pressure, no significant heart disease, able to climb two flights of stairs or walk briskly without chest pain or breathlessness. Treatment can proceed
• 🟡 Intermediate — several risk factors, or uncertain exercise tolerance. Needs cardiac assessment first, often an exercise test
• 🔴 High risk — unstable angina, recent heart attack or stroke within two weeks, uncontrolled arrhythmia, severe valve disease, decompensated heart failure, uncontrolled hypertension. Sexual activity and these drugs are deferred until the cardiac problem is stabilised

💊 The doses, properly

All four drugs work the same way, by amplifying the natural signal. None of them creates desire and none works without sexual stimulation — which is the commonest misunderstanding about them.

Maximum one dose in 24 hours for all of them, except the daily tadalafil regimen.

⏱️ Why they appear not to work

A substantial share of men who report that these drugs failed were never given proper instructions. Before concluding a drug does not work, all six of these need excluding.

1. 🔢 The dose was too low. 50 mg of sildenafil is a starting dose, not a maximum. Many men need 100 mg
2. 🍔 Taken after a large meal. With sildenafil and vardenafil this alone can account for an apparent failure
3. ⏳ Not enough time. Taking sildenafil and attempting intercourse fifteen minutes later will disappoint
4. 🤝 No sexual stimulation. These drugs amplify a signal that has to exist. Waiting for a spontaneous erection to appear will not work
5. 🍷 Alcohol. More than a couple of drinks blunts the response considerably, and dehydration adds dizziness
6. 🔄 Too few attempts. Response improves over the first several uses as anxiety falls. Eight attempts at the maximum tolerated dose is the accepted threshold before calling a drug ineffective

And if one drug genuinely fails after all that, another in the same class may still work. Switching from sildenafil to tadalafil, or the reverse, succeeds often enough to be worth doing before moving to second-line treatment.

🚨 The absolute rules

🏥 Stop and seek care immediately

• 🔴 An erection lasting more than 4 hours — priapism. This is a surgical emergency and permanent damage begins within hours. Do not wait overnight hoping it resolves
• 👁️ Sudden loss or reduction of vision in one or both eyes
• 👂 Sudden hearing loss, with or without ringing or dizziness
• 🫀 Chest pain during or after sexual activity — and tell the emergency team you have taken a PDE5 inhibitor, because it changes which treatments they can use
• 😵 Fainting

Common and harmless effects, for contrast: headache, facial flushing, indigestion, a blocked nose, and with tadalafil back or muscle ache which usually settles after the first few doses.

💊 Medicines that cause it

Worth going through before anything is added, and we include our own products because omitting them would be dishonest.

• 💊 Finasteride and dutasteride — used for prostate enlargement and hair loss. Erectile difficulty and reduced libido occur in a minority and can persist for a period after stopping
• 🧠 SSRI antidepressants — very common and dose-related. Switching to bupropion or mirtazapine usually resolves it
• 🩸 Beta blockers and thiazide diuretics, the two blood pressure classes most associated with it. ACE inhibitors, ARBs and calcium channel blockers are much less so, and a switch is often possible — see our guide to blood pressure treatment
• 💊 Spironolactone, which has anti-androgen activity
• 💊 Opioids, which suppress testosterone strongly with long-term use
• 🧪 Antipsychotics, many of which raise prolactin
• 🚬 Cannabis and heavy alcohol

🧠 When the problem is the loop rather than the arteries

Performance anxiety produces adrenaline, adrenaline narrows blood vessels, and narrowed vessels are the opposite of what an erection requires. One difficult occasion then becomes the thing being monitored on the next, and the monitoring itself prevents the response.

Signs it is this: morning erections present, normal response alone, failure in specific situations, and a clear starting point.

• 🔍 Stop monitoring. Attention directed at whether it is working is itself the interruption. This is the single most useful instruction and the hardest to follow
• 🚫 Deliberately remove the goal for a few weeks — agreed physical contact with intercourse off the table, so there is nothing to fail at. Structured versions of this are a standard and effective therapy
• 💊 A tablet used short term breaks the loop by producing a few reliable experiences, after which the anxiety and often the need for it both fall. That is a legitimate use rather than a crutch
• 🗣️ Tell your partner what is happening. Unexplained avoidance is read as loss of interest almost every time, and that reading does more damage than the original problem
• 📵 Consider the role of pornography in those who respond normally alone and not with a partner
• 🧑‍⚕️ Treat coexisting depression or anxiety, which cap whatever else is tried

🔧 If tablets are not enough

Tablets fail in a minority, particularly after prostate surgery, with advanced diabetes or with severe vascular disease. Other options exist and work, and men are frequently not told about them.

• 💨 Vacuum erection device — a cylinder and pump with a constriction ring. No drugs, no interactions, effective in most men including after surgery. Unromantic and reliable, and usable when every tablet is contraindicated
• 💉 Injection into the penis — alprostadil, self-administered with a very fine needle. Works independently of the nerve signal, which is why it succeeds where tablets do not. Taught in a clinic, with the priapism warning taken seriously
• 💧 Intraurethral alprostadil — a pellet inserted into the urethra. Less effective than injection, less invasive
• ⚙️ Penile implant — surgical, and the option with the highest satisfaction rates of all in properly selected men. Considered when everything else has failed rather than as a last resort to be dreaded
• 🌊 Low-intensity shockwave therapy — still experimental, results inconsistent, frequently sold at high prices by clinics ahead of the evidence. Not unreasonable to ask about; unwise to pay a great deal for

🛡️ A word about counterfeits

Sildenafil and tadalafil are among the most counterfeited medicines in the world. Analyses of products bought from unregulated sources repeatedly find the wrong amount of active ingredient, none at all, or entirely different drugs — including other prescription medicines added without declaration.

The practical consequences are specific rather than vague: a man on nitrates who buys an unlabelled product has no way of knowing he is taking a PDE5 inhibitor, and an unknown dose makes the interaction warnings above impossible to apply. Products should state the active ingredient and its strength, come from a source that asks clinical questions, and arrive in labelled packaging. The whole range here is in the mens health category.

🏃 What changes the underlying problem

Tablets manage the symptom. These change the trajectory, and two of them have effects comparable to medication.

• 🏋️ Aerobic exercise — around 150 minutes a week of moderate activity improves erectile function measurably in trials, through the same mechanism as it improves the rest of the vascular system
• ⚖️ Weight loss, which improves both vascular function and testosterone
• 🚭 Stopping smoking. The effect on small arteries is direct, and improvement follows within months
• 🍷 Less alcohol, both acutely and long term
• 😴 Treating sleep apnea where present
• 🍬 Controlling glucose and blood pressure, which is the whole point of the cardiovascular framing above
• 🚴 Prolonged cycling on a narrow saddle compresses the nerves and vessels in a minority of men; a wider or cut-out saddle resolves it

📞 When to seek help

Emergency:

• An erection lasting over 4 hours
• Sudden vision loss or sudden hearing loss
• Chest pain during or after sex — state that you have taken a PDE5 inhibitor

Promptly:

• New persistent ED, particularly under 50 — ask for a cardiovascular and diabetes assessment, not only a prescription
• Loss of morning erections over weeks
• Chest pain or breathlessness on exertion, before any treatment for ED
• Taking nitrates, including recreationally — do not take these drugs at all
• On an alpha blocker — the dose and timing need setting up properly
• Symptoms starting after a new medicine
• Reduced desire and fatigue alongside — ask for morning testosterone
• Curvature or pain with erection — a different condition requiring assessment
• No benefit after eight attempts at the maximum tolerated dose — ask to switch drug, not to give up
• Low mood or relationship strain, which are common and treatable in their own right

❓ Frequently asked questions

📑 Sources and editorial

• Urological association guidelines on the evaluation and management of erectile dysfunction, including investigation, first-line therapy and second-line options
• Princeton consensus recommendations on cardiovascular risk stratification before treatment for erectile dysfunction and before resuming sexual activity
• Cohort studies of erectile dysfunction as a predictor of subsequent cardiovascular events and the interval between them
• Prescribing information for sildenafil, tadalafil, vardenafil and avanafil, including dosing, food effects, duration, renal and hepatic adjustment and interactions
• Evidence on once-daily tadalafil for erectile dysfunction and for lower urinary tract symptoms due to benign prostatic hyperplasia
• Studies of PDE5 inhibitor non-response attributable to inadequate instruction, and of the number of attempts required before declaring treatment failure
• Safety communications on nitrate and riociguat co-administration, on priapism, on non-arteritic anterior ischaemic optic neuropathy and on sudden sensorineural hearing loss
• Reviews of drug-induced erectile dysfunction, including antihypertensive classes, SSRIs, 5-alpha reductase inhibitors and opioids
• Trials of aerobic exercise and weight loss on erectile function, and reviews of vacuum devices, intracavernosal alprostadil and penile prosthesis outcomes
• Regulatory analyses of counterfeit phosphodiesterase inhibitors purchased outside regulated supply chains
• Related reading: erectile dysfunction and confidence, low libido and testosterone, premature ejaculation, benign prostatic hyperplasia
• Related products: Cialis (Tadalafil), Tadacip (Tadalafil), Sildenafil Citrate, Kamagra, Levitra (Vardenafil), Avana (Avanafil), mens health category
• RXshop Editorial Team — reviewed by Michael Reeves, MD, FACS — Urologist & Men’s Health Specialist