Trial Pack ED

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The Trial Pack ED is a prescription-only medication sampler designed to help men identify the most suitable treatment for erectile dysfunction (ED).

It contains tablets of three different PDE5 (phosphodiesterase type 5) inhibitors: sildenafil, tadalafil, and vardenafil.

Each of these medicines works by the same fundamental mechanism but differs in onset of action, duration of effect, interaction with food, and side-effect profile.

By trying each one on separate occasions under clinical guidance, patients can determine which PDE5 inhibitor provides the best balance of efficacy, tolerability, and convenience for their individual needs.

Erectile dysfunction affects approximately 4.3 million men in the United Kingdom and becomes increasingly prevalent with age, affecting around 40% of men over 40 and up to 70% of men over 70.

ED can have a profound impact on self-esteem, intimate relationships, and overall quality of life. It is also recognised as an independent marker for underlying cardiovascular disease.

This page provides a comprehensive clinical overview of the three PDE5 inhibitors included in the Trial Pack ED, covering how they work, dosing guidance, side effects, safety warnings, and how to obtain a prescription in the UK.

Important safety information about the Trial Pack ED

Before reading further, note the following critical safety points that apply to all three PDE5 inhibitors in this pack.

• Never take a PDE5 inhibitor if you also use nitrate medicines (such as GTN spray or isosorbide tablets) or recreational nitrite "poppers". The combination can cause a dangerous and potentially fatal drop in blood pressure.
• Only take one PDE5 inhibitor at a time. Do not combine sildenafil, tadalafil, and vardenafil or take them on the same day.
• Seek emergency medical help (call 999) if you experience an erection lasting more than 4 hours, sudden loss of vision in one or both eyes, or sudden hearing loss.
• All three medicines require sexual stimulation to work. They do not cause spontaneous erections.

What is erectile dysfunction

Erectile dysfunction is the persistent inability to achieve or maintain an erection sufficient for satisfactory sexual intercourse.

It may be classified as primary (lifelong) or secondary (acquired), and as organic, psychogenic, or mixed in origin.

The majority of ED in men over 40 has an organic basis, most commonly vascular disease resulting from atherosclerosis of the penile arteries.

Other organic causes include neurological conditions (such as multiple sclerosis, spinal cord injury, and diabetic neuropathy), hormonal imbalances (hypogonadism, hyperprolactinaemia, thyroid disorders), medication side effects (antihypertensives, antidepressants, antiandrogens), and surgical or radiation damage to pelvic nerves.

Psychogenic factors, including performance anxiety, depression, relationship difficulties, and stress, may coexist with or exacerbate organic ED.

A comprehensive assessment by a clinician should address both physical and psychological contributing factors.

Risk factors for ED include diabetes mellitus, cardiovascular disease, hypertension, hyperlipidaemia, obesity, smoking, excessive alcohol consumption, and sedentary lifestyle.

The association between ED and cardiovascular disease is well established, and NICE Clinical Knowledge Summaries recommend cardiovascular risk assessment in all men presenting with ED, particularly those aged 40 to 60 years without known cardiac disease.

How erections work

Erection is a neurovascular event.

During sexual arousal, parasympathetic nerve signals cause release of nitric oxide (NO) from non-adrenergic, non-cholinergic (NANC) nerve terminals and endothelial cells in the corpus cavernosum.

NO activates soluble guanylate cyclase, which catalyses the conversion of guanosine triphosphate (GTP) to cyclic guanosine monophosphate (cGMP).

Elevated cGMP causes relaxation of trabecular smooth muscle and dilation of helicine arteries, resulting in increased blood flow into the lacunar spaces of the corpora cavernosa.

The expanding corpora compress the subtunical venular plexus against the tunica albuginea, restricting venous outflow and producing penile rigidity.

Detumescence occurs when cGMP is hydrolysed by PDE5, the predominant phosphodiesterase isoenzyme in penile tissue.

How PDE5 inhibitors work

Sildenafil, tadalafil, and vardenafil are competitive inhibitors of PDE5. By blocking the breakdown of cGMP, they amplify and prolong the normal erectile response to sexual stimulation.

They do not initiate erections independently, and sexual arousal is required for their effect.

All three molecules share this core mechanism but differ in molecular structure, which produces clinically relevant differences in pharmacokinetics and selectivity for other PDE isoenzymes.

Sildenafil

Sildenafil was the first PDE5 inhibitor to be licensed (1998) and remains the most widely prescribed.

It reaches peak plasma concentration within 30 to 120 minutes (median 60 minutes) after oral administration.

The mean terminal half-life is 3 to 5 hours, giving an effective window of approximately 4 to 6 hours.

Absorption is delayed by high-fat meals, which reduce peak concentration by approximately 29%.

Sildenafil has some inhibitory activity against PDE6 in the retina, which accounts for transient visual disturbances (blue tinge, increased light sensitivity) reported by some users.

Tadalafil

Tadalafil has a notably longer half-life of approximately 17.5 hours, providing a therapeutic window of up to 36 hours after a single dose.

This longer duration allows greater spontaneity and has earned tadalafil the designation "the weekend pill".

Peak plasma concentration is reached within 2 hours, and absorption is not affected by food.

Tadalafil is also available as a continuous low-dose daily formulation (2.5 or 5 mg), providing a steady-state therapeutic effect without the need to plan around dosing.

Tadalafil has mild inhibitory activity against PDE11, which is expressed in skeletal muscle and the prostate, potentially explaining the higher incidence of back pain and myalgia.

Vardenafil

Vardenafil is the most potent PDE5 inhibitor in terms of in-vitro IC50 (half maximal inhibitory concentration), though in-vitro potency does not directly translate to superior clinical efficacy at recommended doses.

Onset of action is within 25 to 60 minutes, with a half-life of approximately 4 to 5 hours. Like sildenafil, its absorption is delayed by fatty meals.

At supratherapeutic doses (80 mg), vardenafil has been shown to cause mild QTc prolongation, and it is contraindicated in patients with congenital or acquired QT prolongation and in those taking class IA or III antiarrhythmic agents.

Clinical evidence and guidelines

All three PDE5 inhibitors have been extensively evaluated in randomised controlled trials and are recommended by NICE as first-line pharmacological treatment for erectile dysfunction.

The British Society for Sexual Medicine (BSSM) guidelines emphasise that PDE5 inhibitors should be offered after appropriate assessment and counselling, and that the choice between agents should be based on patient preference, anticipated frequency of sexual activity, tolerability, and comorbidities.

Meta-analyses comparing the three agents show broadly similar efficacy, with response rates (defined as erections sufficient for intercourse) of 60 to 80% across varied populations including men with diabetes, post-prostatectomy patients, and men with spinal cord injuries.

The trial pack approach is endorsed in clinical practice guidelines as a practical method for identifying the optimal agent, since individual responses vary considerably and cannot be predicted from clinical characteristics alone.

How to use the Trial Pack ED

The trial pack approach involves systematically testing each PDE5 inhibitor on separate occasions.

For a fair comparison, each medication should be tried at least four times, as first-dose response is not always representative of ongoing efficacy.

Only take one type of PDE5 inhibitor at a time and never combine two or more in the same 24-hour period.

Keep a brief diary noting which medication you took, the dose, whether you had eaten beforehand, the time to onset of effect, the quality and duration of erection, and any side effects.

This information will help your prescriber make a final recommendation. If one medication produces intolerable side effects, you may stop it and move on to the next.

If none of the three provides a satisfactory response, your prescriber may consider dose optimisation, daily tadalafil, or referral for alternative treatments.

Dosage and administration

Sildenafil

The recommended starting dose is 50 mg, taken approximately 1 hour before anticipated sexual activity.

Based on efficacy and tolerability, the dose may be increased to 100 mg or decreased to 25 mg.

Do not exceed 100 mg in a single dose or take more than one dose per day.

Sildenafil should be taken on a relatively empty stomach for optimal absorption.

Onset of effect is typically within 30 to 60 minutes, and the therapeutic window extends to approximately 4 to 6 hours.

In patients aged 65 years and over, those with hepatic impairment, those with severe renal impairment, or those taking CYP3A4 inhibitors, a starting dose of 25 mg is recommended.

Tadalafil

The recommended starting dose for as-needed use is 10 mg, taken at least 30 minutes before sexual activity.

The dose may be increased to 20 mg or decreased to 5 mg based on individual response. The maximum frequency is one dose per day.

Tadalafil can be taken with or without food. Its prolonged duration of action (up to 36 hours) allows greater flexibility in timing.

For men who anticipate sexual activity at least twice weekly, daily tadalafil 5 mg (or 2.5 mg) provides continuous efficacy without the need for timed dosing.

In patients with moderate renal impairment, the maximum recommended as-needed dose is 10 mg every 48 hours.

Vardenafil

The recommended starting dose is 10 mg, taken 25 to 60 minutes before sexual activity. The dose may be increased to 20 mg or decreased to 5 mg.

Do not exceed 20 mg in a single dose or take more than one dose per day. Vardenafil is best taken on a relatively empty stomach.

In patients aged 65 years and over or those with moderate hepatic impairment, a starting dose of 5 mg is recommended.

Vardenafil is contraindicated in patients taking class IA (quinidine, procainamide) or class III (amiodarone, sotalol) antiarrhythmic medicines.

Side effects of PDE5 inhibitors

Common side effects

Headache is the most frequently reported side effect across all three PDE5 inhibitors, occurring in 10 to 15% of patients. It results from vasodilation of cerebral blood vessels.

Facial flushing (5 to 10%) occurs due to cutaneous vasodilation. Nasal congestion (3 to 10%) results from dilation of nasal mucosal vessels.

Dyspepsia (3 to 7%) may reflect smooth muscle relaxation in the lower oesophageal sphincter.

These effects are dose-dependent, usually mild, and resolve spontaneously within a few hours of onset.

Agent-specific side effects

Sildenafil may cause transient visual disturbances, including a blue-green colour tinge, increased brightness perception, or blurred vision, due to partial inhibition of PDE6 in retinal photoreceptors.

These effects resolve with drug clearance.

Tadalafil is more likely to cause back pain and myalgia (reported in 5 to 6% of patients), which typically begins 12 to 24 hours after dosing and resolves within 48 hours.

Vardenafil carries a low risk of QTc interval prolongation at high doses and should be avoided in patients with pre-existing QT prolongation or those on antiarrhythmic therapy.

Rare but serious adverse events

Priapism (a prolonged, painful erection lasting more than 4 hours) is a urological emergency requiring immediate treatment to prevent permanent ischaemic damage to the corpora cavernosa.

Call 999 or attend A&E if this occurs.

Non-arteritic anterior ischaemic optic neuropathy (NAION) is a rare cause of sudden painless monocular vision loss that has been temporally associated with PDE5 inhibitor use, particularly in men with pre-existing optic disc crowding ("disc at risk").

Sudden sensorineural hearing loss, sometimes accompanied by tinnitus and vertigo, has also been reported rarely.

Discontinue the medication immediately and seek medical advice if you experience any sudden change in vision or hearing.

Warnings and precautions

Absolute contraindications

All three PDE5 inhibitors are absolutely contraindicated in patients taking organic nitrates in any form, including sublingual GTN, transdermal GTN patches, isosorbide mononitrate, isosorbide dinitrate, and recreational amyl or butyl nitrite.

The pharmacodynamic interaction produces additive hypotension that can result in syncope, myocardial infarction, or death.

If a patient using a PDE5 inhibitor requires emergency nitrate therapy (for example, during acute coronary syndrome), a washout period is needed: at least 24 hours after sildenafil or vardenafil, and at least 48 hours after tadalafil.

Cardiovascular considerations

Sexual activity itself carries a modest cardiac risk equivalent to climbing two flights of stairs or brisk walking.

Men with stable cardiovascular disease and good functional capacity can generally use PDE5 inhibitors safely.

However, PDE5 inhibitors are contraindicated or should be used with extreme caution in the following: unstable angina, recent myocardial infarction (within 90 days), recent stroke (within 6 months), uncontrolled hypertension (systolic above 170 mmHg or diastolic above 100 mmHg), hypotension (systolic below 90 mmHg), severe aortic stenosis, hypertrophic obstructive cardiomyopathy, and severe heart failure (NYHA class III or IV).

A cardiovascular risk assessment is an integral part of the prescribing process.

Drug interactions

CYP3A4 inhibitors, including ketoconazole, itraconazole, ritonavir, saquinavir, and erythromycin, increase plasma concentrations of all three PDE5 inhibitors and necessitate dose reduction.

Alpha-adrenoceptor antagonists (tamsulosin, doxazosin, alfuzosin) can potentiate the hypotensive effect; PDE5 inhibitor therapy should be initiated at the lowest dose and alpha-blocker treatment should be stable before starting.

Amlodipine and other antihypertensives may produce additional blood pressure lowering when combined with PDE5 inhibitors, though this is usually clinically insignificant at recommended doses.

Special populations

Elderly patients (65 years and over) are more likely to have comorbidities and polypharmacy, and lower starting doses are generally recommended.

Patients with diabetes mellitus may have reduced PDE5 inhibitor response due to endothelial dysfunction; dose optimisation and lifestyle modification are important.

Patients with hepatic impairment require dose reduction for sildenafil and vardenafil. Patients with severe renal impairment may require reduced doses of sildenafil and tadalafil.

PDE5 inhibitors are not licensed for use in women or in individuals under 18 years of age.

How to obtain the Trial Pack ED in the UK

The Trial Pack ED is a prescription-only medicine (POM) and cannot be purchased over the counter as a combined pack.

To obtain a prescription, you must complete a clinical assessment covering your medical history, current medications, cardiovascular risk factors, and the nature and duration of your erectile dysfunction.

This assessment may be conducted by your GP, a sexual health clinic, or an authorised online prescriber registered with the General Pharmaceutical Council (GPhC) and the Care Quality Commission (CQC).

While sildenafil 50 mg is separately available over the counter as Viagra Connect (a Pharmacy medicine), the trial pack containing all three agents at various strengths requires a prescription.

The standard NHS prescription charge in England is currently 9.90 pounds per item; prescriptions are free in Scotland, Wales, and Northern Ireland.

Private prescriptions may incur additional dispensing fees.

Living with erectile dysfunction: practical guidance

Medication is an important component of ED management, but lifestyle modifications can significantly improve erectile function and overall cardiovascular health.

Evidence-based lifestyle measures include regular aerobic exercise (at least 150 minutes of moderate-intensity activity per week), achieving and maintaining a healthy weight, stopping smoking, reducing alcohol intake to within the recommended 14 units per week, and managing stress and mental health.

Men with diabetes should optimise glycaemic control, as poor blood sugar management accelerates vascular damage.

If depression or anxiety is contributing to ED, cognitive behavioural therapy (CBT) or psychosexual counselling may be beneficial, either alone or alongside pharmacotherapy.

Partner involvement in the treatment process is often helpful. Open communication about ED can reduce performance anxiety and strengthen the relationship.

Some couples find that psychosexual therapy provides lasting benefit beyond what medication alone can achieve.

Your GP can refer you to NHS psychosexual services where available, or you can access services through Relate or the College of Sexual and Relationship Therapists (COSRT).

When to seek urgent medical advice

Call 999 or attend A&E immediately if you experience an erection lasting more than 4 hours (priapism), chest pain during or after sexual activity, sudden loss of vision in one or both eyes, or sudden hearing loss.

Contact your GP or call NHS 111 if you develop persistent headache, dizziness on standing, or any unexpected side effects after taking a PDE5 inhibitor.

Report all suspected adverse reactions via the MHRA Yellow Card scheme at yellowcard.mhra.gov.uk .

Sources

• Sildenafil 50mg Film-Coated Tablets, Summary of Product Characteristics (EMC)
• Tadalafil 10mg Film-Coated Tablets, Summary of Product Characteristics (EMC)
• Vardenafil 10mg Film-Coated Tablets, Summary of Product Characteristics (EMC)
• Erectile Dysfunction, Treatment Summary (BNF)
• Erectile Dysfunction, NICE CKS
• Erectile Dysfunction, NHS
• MHRA Yellow Card Scheme