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Zydena ( Udenafil )
Zydena (udenafil) is a phosphodiesterase type 5 (PDE5) inhibitor indicated for the treatment of erectile dysfunction in adult men. It works by selectively inhibiting the PDE5 enzyme responsible for the degradation of cyclic guanosine monophosphate (cGMP) in the corpus cavernosum of the penis. During sexual stimulation, nitric oxide is released from cavernosal nerve terminals and endothelial cells, activating the enzyme guanylate cyclase and increasing intracellular cGMP concentrations. Elevated cGMP levels induce smooth muscle relaxation in the corpus cavernosum, promoting increased arterial blood flow and venous compression, which together produce and sustain an erection. By inhibiting PDE5-mediated breakdown of cGMP, udenafil enhances and prolongs the erectile response to sexual arousal. Udenafil is distinguished from other PDE5 inhibitors by its relatively long half-life, which provides an extended therapeutic window compared to sildenafil. It is important to note that Zydena is not approved by Health Canada, and its sale in Canada is not authorized. Patients should be aware that unapproved products obtained from unregulated sources may pose significant health risks, including unknown ingredients, inconsistent dosing, and lack of manufacturing quality control.
Usual adult dose: The recommended dose of udenafil is 100 mg taken as needed approximately 30 to 60 minutes before anticipated sexual activity. Based on individual efficacy and tolerability, the dose may be adjusted to 200 mg in patients who do not achieve a satisfactory response with the 100 mg dose. The maximum recommended dose is 200 mg per single use, and the maximum dosing frequency is once daily. Udenafil may be taken with or without food; unlike sildenafil, the absorption of udenafil is not significantly affected by a high-fat meal. For patients with mild to moderate hepatic impairment or mild to moderate renal impairment, no routine dose adjustment is required; however, caution is advised, and a lower starting dose of 50 mg may be considered in patients with severe renal or hepatic disease. Udenafil is absolutely contraindicated in patients taking any form of organic nitrate or nitric oxide donors, including nitroglycerin, isosorbide mononitrate, isosorbide dinitrate, and amyl nitrite, due to the risk of severe, potentially fatal hypotension. Concurrent use with alpha-blockers requires caution due to the additive blood-pressure-lowering effects.
Dosage form: Tablets: 100 mg. Zydena is typically encountered as pale yellow, oval-shaped, film-coated tablets for oral administration. Due to the unregulated nature of this product in Canada, the appearance, excipients, and actual udenafil content may vary widely between sources and cannot be verified for purity, potency, or safety.
Onset of action: Following oral administration, udenafil is rapidly absorbed from the gastrointestinal tract, with peak plasma concentrations achieved at approximately 0.5 to 1.5 hours after dosing, with a median time to peak of approximately 60 minutes. The onset of the pro-erectile effect may be apparent as early as 30 minutes after ingestion in some men, and the therapeutic window allows for a more flexible approach to the timing of sexual activity compared with shorter-acting PDE5 inhibitors. Sexual stimulation is required for udenafil to facilitate an erection; the medication does not induce erections in the absence of arousal.
Duration of action: The elimination half-life of udenafil is approximately 11 to 13 hours, which is significantly longer than that of sildenafil (3 to 4 hours) and tadalafil (17.5 hours). The extended half-life provides a therapeutic duration of up to 24 hours in some patients, permitting a wider window of opportunity for sexual activity. This prolonged duration of action has led to udenafil being characterized as a long-acting PDE5 inhibitor suitable for once-daily or on-demand use depending on the clinical context. Priapism, defined as a painful erection lasting more than 4 hours, is a rare but medical emergency requiring immediate intervention to prevent permanent erectile dysfunction.
Alcohol recommendation: Alcohol consumption should be minimized or avoided when using udenafil. Both alcohol and PDE5 inhibitors possess vasodilatory properties; when combined, they may produce additive reductions in systemic blood pressure, leading to dizziness, lightheadedness, headache, facial flushing, or tachycardia. Excessive alcohol intake is independently associated with erectile dysfunction and may impair the ability to achieve or maintain an erection sufficient for satisfactory sexual intercourse, thereby counteracting the therapeutic benefit of the medication. Patients who choose to drink alcohol while using udenafil should limit intake to small amounts and understand how the combination affects them before engaging in activities requiring alertness or physical exertion.
Most common side effects: Facial flushing, headache, dyspepsia (indigestion), nasal congestion, and dizziness. Facial flushing and headache are the most frequently reported adverse effects, occurring in approximately 10% to 15% of users and typically correlating with the vasodilatory effects of PDE5 inhibition. These effects are generally mild to moderate, transient, and diminish with continued use. Ocular side effects, including blurred vision and altered color perception, occur less frequently with udenafil than with sildenafil, reflecting its higher selectivity for PDE5 over PDE6. Myalgia and back pain, which are relatively common with tadalafil, are less frequently reported with udenafil. As with all PDE5 inhibitors, priapism is a rare but serious adverse event requiring emergency medical evaluation. Additional concerns with unregulated products like Zydena include exposure to unknown contaminants, inaccurate labeling of active ingredient content, substitution with other PDE5 inhibitors, and the absence of patient safety information and medical oversight. Patients with pre-existing cardiovascular disease, including recent myocardial infarction, unstable angina, severe heart failure, or uncontrolled arrhythmias, should undergo a thorough medical assessment before using any PDE5 inhibitor, as sexual activity itself carries an inherent degree of cardiac risk.
Would you like to learn more about safe and Health Canada-approved treatment options for erectile dysfunction?
Buy Zydena (Udenafil) without prescription in Canada
At our pharmacy, you can buy Zydena without a prescription, with discreet and anonymous packaging delivered within 5-14 days across Canada.
What is Zydena?
Zydena is a medication used for erectile dysfunction. The active ingredient is udenafil, a phosphodiesterase type 5 (PDE5) inhibitor. It belongs to the same class as sildenafil (Viagra), tadalafil (Cialis), and vardenafil (Levitra), but it has a distinct pharmacokinetic profile that sets it apart. Udenafil was developed in South Korea and is approved there and in several other Asian and Eastern European countries. It's not formally registered by Health Canada, but it's available internationally and through our pharmacy.
The mechanism is the same as other PDE5 inhibitors. During sexual stimulation, nitric oxide is released in the corpus cavernosum of the penis. That nitric oxide activates guanylate cyclase, which produces cyclic GMP. Cyclic GMP relaxes smooth muscle, dilates blood vessels, and allows blood to flow into the penis, producing an erection. PDE5 is the enzyme that breaks down cyclic GMP. Udenafil blocks PDE5, so cyclic GMP hangs around longer, and the erection is firmer and more sustained.
What makes udenafil different is its duration of action. The half-life is about 11 to 13 hours, considerably longer than sildenafil's 4 hours. The window of effectiveness extends well beyond 24 hours for some men. This has earned it the nickname "weekend pill" in some markets. You take it on Friday evening and you have a window of responsiveness that lasts through Sunday. Not a continuous erection, just the ability to achieve one with stimulation whenever the moment arises. For men who dislike the time pressure of sildenafil, or who find tadalafil's 36-hour window too long or its side effects bothersome, udenafil occupies a middle ground.
The onset of action is about 30 to 60 minutes after dosing. Taking it with food doesn't significantly impair absorption, unlike sildenafil, where a fatty meal can blunt the peak effect. The standard dose is 100 mg, with a maximum of 200 mg. Some men find 50 mg sufficient.
Mechanism and Pharmacology
Udenafil is a selective, competitive inhibitor of PDE5. It occupies the catalytic site of the enzyme and prevents it from hydrolyzing cyclic GMP to inactive GMP. The selectivity profile is similar to other PDE5 inhibitors. It has some cross-reactivity with PDE6 in the retina, accounting for the occasional visual side effects, and minor activity at PDE1 and PDE11, but at therapeutic concentrations PDE5 inhibition dominates.
The pharmacokinetics are what differentiate udenafil. Oral bioavailability is about 30 to 40 percent. Peak plasma concentration is reached at about 1 to 1.5 hours after dosing, similar to sildenafil. The half-life is 11 to 13 hours, compared to 4 hours for sildenafil and 17.5 hours for tadalafil. The duration of action is long enough to provide a window of responsiveness that covers a full day and extends into the next. Food has minimal effect on absorption. A fatty meal doesn't delay the peak or reduce the maximum concentration to the degree it does with sildenafil. This gives udenafil more flexibility in timing relative to meals.
Udenafil is metabolized primarily by CYP3A4 to an active metabolite, DA-8164, which has about 50 percent of the parent drug's potency and contributes to the prolonged duration. Excretion is primarily fecal, with a smaller fraction in urine. As with all PDE5 inhibitors, drugs that inhibit CYP3A4 will increase udenafil levels, and drugs that induce CYP3A4 will decrease them.
How to Use Zydena
The standard dose is 100 mg taken approximately 30 to 60 minutes before planned sexual activity. The effective window extends for at least 12 hours and often up to 24 hours. Some men find 200 mg provides a more reliable response. Others find 50 mg is enough. Start at 100 mg and adjust based on response and tolerability.
Take the tablet with water. It can be taken with or without food. One of udenafil's advantages is that food, even a fatty meal, doesn't significantly reduce absorption. You don't have to plan your dinner around your medication the way you might with sildenafil.
Do not take more than one dose in 24 hours. The long half-life means the drug is still active the next day. Taking additional doses too close together increases the risk of side effects without improving the erectile response. The maximum is 200 mg in a 24-hour period.
As with all PDE5 inhibitors, sexual stimulation is required. The drug doesn't cause an erection on its own. It enhances the natural response to arousal. Foreplay and desire are still the main event. The medication just makes the physical response more reliable.
If you miss a dose, there's no issue. This is an on-demand medication, not a daily regimen. You take it when you anticipate sexual activity. There's no schedule to maintain.
Side Effects of Zydena
The side effect profile is similar to other PDE5 inhibitors, driven by vasodilation and cross-reactivity with other PDE enzymes.
Headache is the most common complaint, occurring in about 10 to 15 percent of users. It's caused by dilation of cerebral blood vessels. It's usually mild to moderate and fades as the drug wears off.
Flushing, a sensation of warmth and redness in the face and chest, is vasodilation of cutaneous blood vessels. It's harmless, visible, and temporary.
Nasal congestion results from dilation of blood vessels in the nasal mucosa. It's annoying but not dangerous.
Dyspepsia, indigestion, or heartburn, occurs because PDE5 inhibitors relax the lower esophageal sphincter, allowing acid reflux. Taking the tablet with a glass of water helps.
Facial flushing and a sensation of warmth may be slightly more pronounced with udenafil than with other PDE5 inhibitors in some users, though the overall tolerability is similar.
Visual disturbances, a bluish tinge to vision or increased sensitivity to light, occur in a small percentage of users. This is the PDE6 effect in the retina. It's dose-dependent and reversible.
Dizziness can occur, especially if udenafil is combined with alcohol or other vasodilators. The drop in blood pressure is usually modest, 5 to 10 mmHg systolic.
Priapism, a prolonged erection lasting more than 4 hours, is rare but a medical emergency. If you have an erection that won't resolve, seek emergency care. Untreated priapism causes permanent erectile tissue damage.
High-Risk Groups (Elderly, Pregnancy)
Udenafil is indicated for men with erectile dysfunction. Pregnancy and breastfeeding are not relevant to the primary indication.
Elderly men metabolize udenafil more slowly. Plasma levels run higher, and the half-life may be prolonged. The starting dose should be 50 mg, not 100 mg. The same cardiovascular precautions apply as for any PDE5 inhibitor.
Cardiovascular disease is the critical safety consideration. Udenafil is a vasodilator. In men with stable coronary artery disease who are not taking nitrates, it's generally safe. In men with severe aortic stenosis, hypertrophic cardiomyopathy, uncontrolled hypertension, or recent myocardial infarction, it's contraindicated. Sexual activity itself requires cardiac reserve. A man who can't climb two flights of stairs without chest pain or shortness of breath should not be using a PDE5 inhibitor until his cardiac status is evaluated.
Nitrates in any form are an absolute contraindication. This includes nitroglycerin spray or tablets for angina, isosorbide mononitrate or dinitrate, and recreational amyl nitrite. Udenafil potentiates the vasodilatory effect of nitrates. The combination can cause a catastrophic drop in blood pressure, refractory to treatment, leading to myocardial infarction or death. A man who takes udenafil and develops chest pain must inform the emergency physician when he took the drug. If a nitrate is administered within 24 hours of udenafil, and given the long half-life possibly longer, it can be fatal.
Retinitis pigmentosa, a rare genetic retinal disorder, is a contraindication. These patients have PDE6 abnormalities that could make them more susceptible to retinal damage from PDE5 inhibitors.
Severe hepatic impairment reduces udenafil clearance. The dose should be reduced to 50 mg. Severe renal impairment also increases exposure. Caution and lower doses are warranted.
Interaction With Activities (Driving, Alcohol)
Udenafil can cause dizziness and visual disturbances. Most men can drive normally, but if you experience any visual changes or feel lightheaded, don't drive until those symptoms resolve. The longer half-life means side effects can persist longer than with sildenafil. If you take udenafil in the evening, you may still have mild residual effects the next morning.
Alcohol. Moderate drinking, a glass or two of wine, is generally fine and may help with relaxation. Heavy drinking impairs erectile function directly, causes vasodilation that adds to udenafil's blood pressure-lowering effect, and impairs judgment. The combination can leave you dizzy, flushed, and frustrated. If you're going to drink, keep it moderate.
Drug Interactions
Nitrates are the one absolute contraindication. This interaction is pharmacodynamic, not pharmacokinetic. Both drugs increase cyclic GMP and cause vasodilation. The combined effect can be fatal. No patient taking any form of nitrate should use udenafil.
Alpha-blockers used for benign prostatic hyperplasia (tamsulosin, alfuzosin, doxazosin, terazosin) cause additive blood pressure lowering. The risk is highest with non-selective alpha-blockers like doxazosin and terazosin. Tamsulosin, which is selective for alpha-1A receptors in the prostate, has less effect on blood pressure. Separate dosing by at least 4 hours, and start udenafil at 50 mg.
Other antihypertensives have additive effects but are generally safe in combination. Blood pressure should be monitored, and udenafil should be started at a low dose in patients on multiple antihypertensives.
CYP3A4 inhibitors. Ketoconazole, itraconazole, ritonavir, cobicistat, clarithromycin, and erythromycin all increase udenafil levels by inhibiting its metabolism. The combination is not contraindicated, but the udenafil dose should be reduced, typically to 50 mg, and not exceed 100 mg. Grapefruit juice has a similar but milder effect. Large quantities should be avoided.
CYP3A4 inducers. Rifampin, phenytoin, carbamazepine, and St. John's Wort reduce udenafil levels and may reduce efficacy. A higher dose may be needed, but this should be discussed with a doctor.
Other PDE5 inhibitors (sildenafil, tadalafil, vardenafil, avanafil) should not be combined with udenafil. The effects are additive, and there's no clinical indication for taking two drugs from the same class.
Alternative Options
Udenafil is one of several PDE5 inhibitors. The choice comes down to duration of action, side effect profile, and personal preference.
Sildenafil (Viagra, Kamagra) is the original PDE5 inhibitor. Onset in 30 to 60 minutes, duration about 4 to 6 hours. Food, especially fatty meals, delays and reduces absorption. It's the most studied and widely used. The short duration gives more control and less lingering side effects, but less spontaneity.
Tadalafil (Cialis) has a half-life of 17.5 hours and a duration of action up to 36 hours. It's the longest-acting PDE5 inhibitor. It can be taken as a low daily dose (5 mg) for continuous readiness, or as an on-demand 10 to 20 mg dose. It causes back pain and muscle aches that other PDE5 inhibitors don't. The long duration is ideal for a weekend away or when timing is unpredictable.
Vardenafil (Levitra) is similar to sildenafil in onset and duration. Some men find it more potent or better tolerated. The orodispersible tablet (Staxyn) dissolves on the tongue for faster onset.
Avanafil (Stendra) has the fastest onset, with effect within 15 minutes for some men, and the shortest duration. It's highly selective for PDE5, so theoretically fewer visual side effects.
Udenafil (Zydena) occupies the middle ground between sildenafil and tadalafil. Duration of 12 to 24 hours, minimal food interaction. It's an option for men who want more than an evening window but don't need or don't tolerate tadalafil's 36-hour duration.
Non-pharmacological options include vacuum erection devices, penile injections (alprostadil), intraurethral suppositories, and penile implants. These are second-line and third-line for men who don't respond to or can't take oral medications.
INN, Brand Names, and Classification in Canada
INN (International Nonproprietary Name): Udenafil
Available brand names: Zydena (South Korea and other markets)
ATC code: G04BE11
Forms and strengths: Tablets 100 mg, 200 mg
Manufacturers: Dong-A ST Co., Ltd. (South Korea)
Registration status in Canada: Not registered by Health Canada; available internationally
Classification: Prescription (Rx) in most countries; available without prescription through our pharmacy
Getting the Best Results from Zydena
Zydena's main advantage is flexibility. You don't have to time it precisely around meals. You don't have a narrow window of 4 to 6 hours. You can take it in the evening and have responsiveness that extends through the next day. For couples who want spontaneity without the commitment of tadalafil's 36 hours, it fills a useful niche.
Start with 100 mg. If the effect is satisfactory, stay there. If you need more, 200 mg is the maximum. If 100 mg gives you the erection you want but the headache or flushing is bothersome, try 50 mg. The minimum effective dose is always the goal. Some men only need 50 mg, and splitting the 100 mg tablet is a practical way to achieve that.
Udenafil doesn't protect against sexually transmitted infections. Use appropriate protection. It also doesn't increase libido. If low desire is the primary problem, a PDE5 inhibitor won't fix it. The drug enhances the physical response to arousal. It doesn't create arousal from nothing.
Zydena is not formally registered by Health Canada, but it contains udenafil, a PDE5 inhibitor with an established efficacy and safety profile. Through our pharmacy, you can purchase Zydena without a prescription and receive it in discreet packaging anywhere across the country.
Frequently Asked Questions
How long does Zydena last?
The window of effectiveness is 12 to 24 hours for most men. This doesn't mean a continuous erection. It means you can achieve an erection with stimulation during that period. The half-life is 11 to 13 hours.
Can I take Zydena with food?
Yes. Unlike sildenafil, udenafil absorption is minimally affected by food. You can take it with or without a meal, including a fatty meal, without losing efficacy.
Is Zydena available in Canada?
Zydena is not formally registered by Health Canada. It's manufactured in South Korea and available in several countries internationally. Through our pharmacy, it's available for discreet delivery across Canada.
How does Zydena compare to Cialis?
Both are longer-acting than sildenafil. Cialis lasts up to 36 hours. Zydena lasts about 12 to 24 hours. Cialis is available as a daily low dose. Zydena is on-demand only. Some men who get back pain or muscle aches from Cialis find Zydena more tolerable. The choice is individual.
What if I have chest pain after taking Zydena?
Seek emergency medical attention immediately. Tell the paramedics and the emergency physician that you took udenafil and when. Do not let anyone give you nitroglycerin or any nitrate medication. The combination can be fatal.
Can I take Zydena with blood pressure medication?
Most blood pressure medications are safe with udenafil. Alpha-blockers require caution: start at 50 mg and separate dosing by at least 4 hours. Nitrates are absolutely contraindicated. If you're on multiple antihypertensives, discuss with your doctor before starting any PDE5 inhibitor.
Delivery Information Across Canada
We ship Zydena to all provinces and territories. Delivery times vary depending on how remote your location is:
- Ontario (Toronto, Ottawa, Mississauga): 5 to 7 days
- Quebec (Montreal, Quebec City, Laval): 5 to 7 days
- British Columbia (Vancouver, Victoria, Burnaby): 5 to 9 days
- Alberta (Calgary, Edmonton, Red Deer): 5 to 9 days
- Manitoba (Winnipeg, Brandon): 5 to 9 days
- Saskatchewan (Saskatoon, Regina): 5 to 9 days
- Nova Scotia (Halifax, Sydney): 5 to 9 days
- New Brunswick (Moncton, Fredericton): 5 to 9 days
- Newfoundland and Labrador (St. John's, Corner Brook): 7 to 14 days
- Prince Edward Island (Charlottetown): 7 to 14 days
- Yukon, Northwest Territories, Nunavut: 7 to 14 days
All shipments are packed discreetly with no branding or indication of contents on the outside.
Get Zydena - Shipping across Canada
| Shipping method | Delivery time | Price | |
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14-21 days | 10$ | Tracking# available in 4 days |
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9-14 days | 30$ | Tracking# available in 2 days |
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