Cialis Professional (Tadalafil 20mg/40mg)

Medically reviewed by Dr. Sarah Mitchell, RPh, Clinical Pharmacist — Updated April 2026

What Is Tadalafil (Cialis Professional)? — Complete PDE5 Mechanism

Tadalafil is a selective, reversible inhibitor of phosphodiesterase type 5 (PDE5) — the same enzyme class as sildenafil and vardenafil, but with distinct selectivity, pharmacokinetics, and clinical profile.

The NO-cGMP-PDE5 pathway — how tadalafil produces erection:

• Sexual stimulation triggers nitric oxide (NO) release from parasympathetic nerve terminals and endothelial cells in the penile corpora cavernosa
• NO activates guanylate cyclase → cGMP synthesis: Nitric oxide activates the enzyme guanylate cyclase, producing cyclic guanosine monophosphate (cGMP) in penile smooth muscle cells
• cGMP causes smooth muscle relaxation → arterial vasodilation → erection: cGMP activates protein kinase G (PKG), causing relaxation of arterial and trabecular smooth muscle in the corpora cavernosa, allowing arterial blood to flow in under pressure, producing engorgement and rigidity
• PDE5 normally degrades cGMP, ending the erection. Tadalafil competitively inhibits PDE5, preventing cGMP breakdown — prolonging and amplifying the smooth muscle relaxation and erectile response

Why tadalafil's 36-hour window is pharmacologically unique: The duration of PDE5 inhibitor action is primarily determined by the plasma half-life of the drug. Sildenafil has a half-life of 3 to 5 hours; vardenafil 4 to 5 hours. Tadalafil has a plasma half-life of approximately 17.5 hours — more than three times longer than sildenafil. This means effective plasma concentrations capable of PDE5 inhibition persist for up to 36 hours after a single dose. Crucially, this 36-hour window does not mean a continuous erection for 36 hours — it means that within any 36-hour window after dosing, normal sexual stimulation can trigger an erectile response. Between episodes of arousal, the penis is completely flaccid.

Tadalafil's selectivity advantage: Tadalafil is highly selective for PDE5 vs PDE6 (the retinal enzyme) — approximately 1,000-fold selectivity. Sildenafil has approximately 10-fold selectivity for PDE5 vs PDE6. This greater PDE6 selectivity means tadalafil causes significantly fewer visual side effects (the blue-green colour tinge and light sensitivity seen with sildenafil) — an important practical advantage that many Canadian patients notice when switching between PDE5 inhibitors.

What Makes Cialis Professional Different from Standard Cialis Generic?

Canadian patients frequently ask how Cialis Professional differs from standard Cialis Generic (tadalafil 10mg/20mg) available on the site:

The sublingual (under-tongue) administration advantage: Cialis Professional tablets are designed for sublingual or buccal absorption — placed under the tongue and allowed to dissolve rather than swallowed. Sublingual administration bypasses hepatic first-pass metabolism (the initial liver processing that reduces bioavailability of swallowed tablets), achieving faster peak plasma concentrations — typically 15 to 30 minutes vs 30 to 45 minutes for standard oral tadalafil. This faster onset is particularly valued by Canadian men who prefer more spontaneous rather than planned intimacy.

Health Canada-Approved Tadalafil Indications

1. Erectile Dysfunction (ED) — Primary Indication

Tadalafil is approved by Health Canada for the treatment of erectile dysfunction in adult men — both for on-demand use (10mg or 20mg taken before sexual activity, up to once daily) and for daily low-dose use (2.5mg or 5mg once daily). Cialis Professional at 20mg and 40mg is specifically for on-demand use in men seeking higher-dose tadalafil therapy.

2. Benign Prostatic Hyperplasia (BPH) — The Second Canadian Indication

Tadalafil 5mg once daily is the only PDE5 inhibitor approved by Health Canada for benign prostatic hyperplasia — the non-cancerous prostate enlargement that causes urinary symptoms (weak urine stream, urinary urgency, nocturia, incomplete bladder emptying) in a majority of Canadian men over 50. This dual indication makes tadalafil uniquely valuable for the large Canadian population of men who have both ED and BPH simultaneously — two of the most prevalent conditions in aging Canadian males. The mechanism: PDE5 is expressed in the smooth muscle of the prostate, urethra, and bladder — tadalafil-mediated PDE5 inhibition relaxes these smooth muscle structures, improving urinary flow and reducing BPH symptoms. Note: the 20mg and 40mg doses in Cialis Professional are not the doses used for BPH management; BPH treatment uses tadalafil 5mg daily. However, men with both ED and BPH can discuss comprehensive tadalafil dosing strategies with their Canadian physician.

Cialis Professional vs Other PDE5 Inhibitors — The Canadian Comparison

Canadian Dosing Guide

On-demand use (Cialis Professional):

• Standard starting dose: 20mg tadalafil taken as a sublingual tablet approximately 15 to 30 minutes before anticipated sexual activity
• High-dose option: 40mg for men who have not achieved satisfactory response at 20mg — only under physician guidance, as 40mg exceeds Health Canada's standard approved maximum
• Maximum: one tablet per 24-hour period regardless of dose strength
• Sexual stimulation is required — Cialis Professional does not produce an erection without arousal

How to take the sublingual tablet:

• Place the tablet under the tongue and allow it to dissolve completely — do not swallow, crush, or chew
• Dissolution typically takes 1 to 3 minutes
• Avoid eating or drinking for a few minutes after sublingual administration to allow complete mucosal absorption
• Can be taken with or without food — tadalafil has minimal food interaction regardless of administration route

Alcohol — important guidance: Tadalafil combined with significant alcohol consumption increases hypotensive risk. Moderate alcohol consumption (1 to 2 standard drinks) is generally acceptable; heavy drinking (5+ drinks) combined with tadalafil substantially increases dizziness and syncope risk. Unlike sildenafil, tadalafil's longer half-life means alcohol interactions can occur many hours after dosing.

Dose adjustments:

• Men over 65: standard pharmacokinetics are not significantly altered by age for tadalafil; start with 20mg and assess response
• Severe hepatic impairment (Child-Pugh Class C): tadalafil is not recommended
• Severe renal impairment (CrCl <30 mL/min) or end-stage renal disease on dialysis: maximum dose 10mg; tadalafil not recommended for daily use
• CYP3A4 inhibitors (ritonavir, ketoconazole, clarithromycin): reduce tadalafil dose to maximum 10mg per 72 hours — these drugs substantially increase tadalafil plasma levels

Absolute Contraindications — When Cialis Professional Must NOT Be Taken

1. Nitrates in any form — ABSOLUTE CONTRAINDICATION, potentially fatal: Tadalafil combined with organic nitrates or nitrite compounds causes severe, uncontrolled hypotension that can produce myocardial infarction, stroke, and death. The interaction is potentially more dangerous than with shorter-acting PDE5 inhibitors because tadalafil's 36-hour action window means the nitrate interaction risk persists for up to 48 hours after the last tadalafil dose. Contraindicated nitrate medications include: all nitroglycerin/glyceryl trinitrate (GTN) preparations — sublingual tablets (Nitrostat), sprays (Nitrolingual), patches, IV infusions; isosorbide mononitrate (Imdur); isosorbide dinitrate (Isordil); amyl nitrite and butyl nitrite (recreational "poppers"). If you use recreational poppers in sexual contexts — do not take Cialis Professional under any circumstances. If emergency nitrate treatment is needed for chest pain after tadalafil use, alert emergency personnel about tadalafil use and timing.

2. Significant cardiovascular disease: Recent myocardial infarction (within 90 days), recent stroke (within 6 months), unstable or resting angina, uncontrolled hypertension, severe heart failure (NYHA Class III/IV), or haemodynamic instability. Tadalafil's 36-hour duration means cardiovascular effects persist much longer than with shorter-acting PDE5 inhibitors — making cardiovascular pre-screening particularly important.

3. Hypersensitivity to tadalafil

4. Severe hepatic impairment (Child-Pugh Class C)

5. Recent use of another PDE5 inhibitor: Do not combine Cialis Professional with sildenafil, vardenafil, or avanafil. Given tadalafil's 36-hour half-life, allow at least 48 hours between the last tadalafil dose and any other PDE5 inhibitor.

Side Effects — Complete Canadian Guide

Very common / common (≥1% of patients):

• Headache: Most common side effect — caused by cerebral vasodilation. Typically mild to moderate; resolves within a few hours. Acetaminophen (Tylenol) can be used for relief
• Flushing: Facial redness and warmth — vasodilatory effect; common, mild, transient
• Nasal congestion / rhinorrhoea: Vasodilation of nasal mucosa; common, self-limiting
• Dyspepsia / heartburn: Relaxation of lower oesophageal sphincter smooth muscle; taking with food or antacids may help
• Back pain and muscle aches (myalgia) — unique to tadalafil: One of the most clinically distinctive features of tadalafil compared to other PDE5 inhibitors. Back pain and diffuse myalgia (aching in the back, legs, and sometimes arms) occurs in approximately 6 to 7% of tadalafil users — substantially more frequently than with sildenafil or vardenafil. The mechanism is not fully elucidated but appears related to tadalafil's inhibition of PDE11A — a phosphodiesterase expressed in skeletal muscle and the testes. The back pain typically occurs 12 to 24 hours after dosing, is usually mild to moderate in severity, and resolves within 48 hours without specific treatment. Over-the-counter analgesics help. This side effect is particularly notable with the longer half-life of tadalafil — patients should be counselled about it in advance to avoid unnecessary concern. Tadalafil-related back pain is not associated with spinal or disc pathology and does not indicate a serious adverse event
• Dizziness and lightheadedness: Blood pressure-lowering effect; more pronounced with alcohol co-ingestion, alpha-blockers, antihypertensives, or at the 40mg dose

Important — visual and hearing effects:

• Visual disturbances: Tadalafil's high PDE6 selectivity means colour vision changes (blue-green tinge) and light sensitivity are substantially less frequent with tadalafil than with sildenafil. Visual side effects with tadalafil are uncommon but can occur, particularly at higher doses
• Non-arteritic anterior ischaemic optic neuropathy (NAION): Rare cases of sudden vision loss or impairment reported with tadalafil, as with all PDE5 inhibitors. Risk factors: age >50, pre-existing optic nerve crowding, diabetes, hypertension, smoking, hyperlipidaemia. If sudden vision change occurs after taking Cialis Professional — stop the medication immediately and seek emergency ophthalmology evaluation. Vision loss from NAION may be permanent
• Sudden hearing loss: Rare; sudden decrease or loss of hearing, tinnitus. Stop medication and seek emergency ENT evaluation immediately if this occurs

Serious — requiring immediate medical attention:

• Priapism: Prolonged erection lasting more than 4 hours — a urological emergency. Immediate emergency care required; permanent erectile dysfunction results from untreated priapism within 4 to 6 hours
• Severe hypotension: Particularly with nitrates (absolutely contraindicated), alpha-blockers without appropriate separation, heavy alcohol, or in men with cardiovascular disease

Key Drug Interactions

• Nitrates (ALL forms) — ABSOLUTELY CONTRAINDICATED, persistent risk for 48h post-dose: GTN/nitroglycerin, isosorbide mononitrate/dinitrate, amyl nitrite/poppers. Fatal hypotension risk. No safe combination. The 36-hour half-life of tadalafil means this risk extends well beyond the immediate dosing period
• Alpha-blockers (tamsulosin/Flomax, alfuzosin/Xatral, doxazosin, terazosin) — significant interaction in Canadian men with BPH: Alpha-blockers are widely prescribed to Canadian men over 50 for BPH/enlarged prostate — the same population that frequently has concurrent ED. Both alpha-blockers and tadalafil lower blood pressure; combination can cause symptomatic orthostatic hypotension (dizziness on standing, syncope). If alpha-blockers are being used, tadalafil therapy should begin at the lowest dose and be initiated at a stable alpha-blocker dose. Tamsulosin (Flomax) — the most commonly prescribed alpha-blocker in Canada — has a lower hypotension interaction risk with tadalafil than other alpha-blockers. Discuss with your Canadian physician or pharmacist
• Strong CYP3A4 inhibitors (ritonavir, ketoconazole, itraconazole, clarithromycin, erythromycin, grapefruit juice): These drugs inhibit tadalafil's hepatic metabolism, substantially increasing plasma levels. With ritonavir (HIV treatment), tadalafil dose must not exceed 10mg per 72 hours. Avoid large quantities of grapefruit juice on the day of dosing
• CYP3A4 inducers (rifampicin, carbamazepine, phenytoin, St. John's Wort): These drugs accelerate tadalafil metabolism — substantially reducing plasma levels and potentially reducing efficacy. Higher doses may not adequately compensate; discuss with physician
• Antihypertensive medications: Additive blood pressure reduction; monitor for hypotensive symptoms, particularly with calcium channel blockers (amlodipine), ACE inhibitors, and beta-blockers. Very common co-prescription scenario in Canadian men with hypertension and ED
• Other PDE5 inhibitors: Never combine; allow 48+ hours between tadalafil and other PDE5 inhibitor use
• Alcohol (≥5 standard drinks): Significant additive hypotension; avoid heavy drinking for the entire 36-hour tadalafil action window

Delivery to All Canadian Provinces and Territories

drugs-canada.com ships Cialis Professional discreetly to all Canadian provinces and territories. Standard delivery: 4–9 business days.

Ontario (Toronto, Ottawa, Hamilton, London, Brampton, Mississauga, Kitchener-Waterloo) — Quebec (Montreal, Quebec City, Laval, Gatineau, Sherbrooke) — British Columbia (Vancouver, Surrey, Burnaby, Victoria, Kelowna, Abbotsford) — Alberta (Calgary, Edmonton, Red Deer, Lethbridge) — Manitoba (Winnipeg, Brandon) — Saskatchewan (Saskatoon, Regina) — Nova Scotia (Halifax, Sydney) — New Brunswick (Moncton, Saint John, Fredericton) — Newfoundland and Labrador (St. John's, Corner Brook) — Prince Edward Island (Charlottetown) — Northwest Territories (Yellowknife) — Yukon (Whitehorse) — Nunavut (Iqaluit).

All orders are dispatched in plain, unmarked packaging with no reference to the contents or sender. Every order includes a tracking number.

Frequently Asked Questions — Cialis Professional (Tadalafil) in Canada

Why does Cialis (tadalafil) last 36 hours while Viagra only lasts 4–5 hours? The difference is entirely pharmacokinetic. Tadalafil has a plasma half-life of approximately 17.5 hours — more than three times longer than sildenafil's 3 to 5 hour half-life. This means effective concentrations of tadalafil capable of inhibiting PDE5 remain in the bloodstream for up to 36 hours after a single dose. Importantly, this does not mean a continuous erection for 36 hours — it means that sexual stimulation during any point within that 36-hour window can trigger a normal erectile response. Between moments of arousal, the penis is completely flaccid. This extended window eliminates the "scheduling" pressure associated with shorter-acting PDE5 inhibitors, allowing sexual activity to occur spontaneously when the moment is right.

What causes back pain and muscle aches with Cialis and how long does it last? Back pain and diffuse myalgia are unique side effects of tadalafil not typically seen with sildenafil or vardenafil. They occur in approximately 6 to 7% of users, typically developing 12 to 24 hours after dosing and resolving within 48 hours. The likely mechanism is tadalafil's inhibition of PDE11A — a phosphodiesterase expressed in skeletal muscle and reproductive tissue. The back pain is not dangerous, is not related to spinal disc pathology, and resolves spontaneously. Acetaminophen or ibuprofen can provide relief. If you experience back pain after Cialis Professional, this is a known and manageable side effect — not a reason for alarm. However, if the pain is severe, accompanied by fever, or involves urinary symptoms, consult a physician to rule out other causes.

Can I take Cialis Professional if I'm on tamsulosin (Flomax) for my prostate? This is one of the most important drug interaction questions for Canadian men over 50, since both ED and BPH are extremely common in this age group. Tamsulosin (Flomax) and tadalafil can generally be combined — tamsulosin has a lower blood pressure interaction risk with tadalafil than other alpha-blockers. However, blood pressure can still decrease with the combination, particularly with higher tadalafil doses such as the 40mg in Cialis Professional. Your Canadian physician or pharmacist should review this combination before starting Cialis Professional and recommend the appropriate dose. Many Canadian urologists and family physicians regularly manage patients on both tamsulosin and tadalafil successfully.

What is the difference between Cialis Professional 40mg and standard Cialis Generic 20mg? Cialis Professional contains either 20mg or 40mg tadalafil in a sublingual (under-tongue) formulation, compared to standard Cialis Generic oral tablets (10mg/20mg). Sublingual administration provides faster onset (15–30 min vs 30–45 min) by bypassing hepatic first-pass metabolism. The 40mg dose is twice the standard maximum approved by Health Canada and is intended for men with significant or refractory ED who have not achieved adequate response at 20mg — only under physician guidance. Both products have the same 36-hour duration of action.

How long does delivery to Canada take? Standard delivery to all Canadian provinces and territories takes 4 to 9 business days. All orders arrive in plain, unmarked packaging with no reference to the contents or sender. Every order includes a tracking number.

All information on this page is for general informational purposes only and does not constitute medical advice. Cialis Professional (Tadalafil) is a prescription medicine in Canada — a valid prescription from a licensed Canadian healthcare provider is required. The 40mg dose exceeds Health Canada's standard maximum approved tadalafil dose of 20mg for erectile dysfunction; individual physician assessment is essential. Tadalafil is absolutely contraindicated with nitrates in any form, including recreational nitrites ("poppers"). If you experience sudden vision loss, sudden hearing loss, chest pain, or priapism (erection lasting more than 4 hours), seek emergency medical care immediately. Always consult a qualified Canadian physician before starting any medication for erectile dysfunction.