40 mg, so it is good value when used in halves or quarters
Phosphodiesterase type 5 (PDE5) inhibitors widely used to treat ED (erectile dysfunction) include sildenafil (brand name: Viagra), tadalafil (brand name: Cialis) and vardenafil (brand name: Levitra). These drugs have similar mechanisms of action, but differ in duration of action, timing of dosing and side effects. The features of each are compared and explained below.
1. Tadalafil (Cialis)
Tadalafil is a type of PDE5 inhibitor primarily used as a treatment for ED (erectile dysfunction). The most well-known brand name is Cialis. Tadalafil may also be prescribed for conditions such as benign prostatic hyperplasia (BPH) and pulmonary arterial hypertension (PAH). Below, we provide detailed information about the characteristics and usage of Tadalafil.
1. Mechanism of Action
Tadalafil works by inhibiting the PDE5 (phosphodiesterase type 5) enzyme. PDE5 is responsible for breaking down cGMP, a substance that causes the blood vessels in the penis to constrict. By inhibiting PDE5, Tadalafil promotes the relaxation of the smooth muscles in the penis, increasing blood flow and making it easier to achieve an erection.
This mechanism allows Tadalafil to have a stimulating effect on erections when sexual arousal occurs, but it does not cause an erection in the absence of sexual stimulation.
2. Duration
One of the standout features of Tadalafil is its exceptionally long duration of action. The effects of Tadalafil last for approximately 24 to 36 hours after taking it. This duration is significantly longer compared to other ED medications like Viagra (Sildenafil) and Levitra (Vardenafil). As a result, it is sometimes referred to as a “weekend pill,” allowing for greater flexibility in timing for users.
3. Dosage
Tadalafil can be taken either as a on-demand dose (about one hour before sexual activity) or as a daily dose (a consistent amount taken every day). With daily dosing, individuals can engage in sexual activity more naturally, and the effects are more stable.
Medicines that should not be taken together
- Nitrates (e.g. nitroglycerin)
- This applies to drugs such as nitroglycerin, isosorbide dinitrate and amylnitrite.
- Riociguat (Treatment of pulmonary arterial hypertension)
- Alpha-blockers (e.g. doxazosin, tamsulosin)
- Ketoconazole and Ritonavir
What to watch out for while taking it
- Alcohol Consumption
- Grapefruit Juice
4. Diseases for which a particular medicine is indicated
Tadalafil is used for the following conditions:
- ED (erectile dysfunction): Used when maintaining an erection is difficult.
- BPH (benign prostatic hyperplasia): Relief of symptoms such as dysuria and frequent urination.
- PAH (pulmonary arterial hypertension ): Lowers blood pressure in the lungs and reduces strain on the heart.
5. Side Effect
Common side effects reported include:
- Headaches
- Indigestion
- Myalgia
- Backache
- Nasal congestion
These side effects are usually mild and temporary, but in rare cases, serious side effects may occur. Examples include vision changes and prolonged erection (known as priapism). If any of these symptoms arise, it is important to consult a doctor immediately.
6. Contraindications and Precautions
Tadalafil is contraindicated in the following situations:
- Patients using nitrate medications: Combining Tadalafil with nitrate medications used for treating heart disease can lead to a risk of severe blood pressure drops.
- Patients with severe liver or kidney disease
If there is a history of heart disease, a doctor should be consulted before use.
7. Comparison with other ED Drugs
Tadalafil is often compared to other PDE5 inhibitors, such as Sildenafil (Viagra) and Vardenafil (Levitra). Its most notable feature is its long duration of action, making it an optimal choice for those seeking flexibility in timing. In contrast, Viagra and Levitra tend to take effect more quickly than Tadalafil.
Half-life of Tadalafil (Tadalafil)
Tadalafil has a half-life of approximately 17.5 hours. This is considerably longer than other ED medications, indicating that the drug remains in the body for an extended period. As a result of this long half-life, its effects can last for 24 to 36 hours, providing flexibility for engaging in sexual activity long after taking the medication.
In comparison to other PDE5 inhibitors, for instance, Sildenafil (Viagra) has a half-life of about 4 to 5 hours, highlighting the extended duration of action of Tadalafil.
The long half-life of Tadalafil makes it suitable not only for on-demand use but also for daily dosing (taking a small amount each day to maintain its effects). This allows for a more natural timing for sexual activity, providing added convenience.
Opinion of the Japanese Urological Association
The Japanese Urological Association recommends tadalafil (brand name Cialis) for the treatment of ED (erectile dysfunction) and benign prostatic hyperplasia (BPH). In particular, tadalafil was approved in 2014 for the treatment of benign prostatic hyperplasia (BPH) and has been shown to be effective not only in treating ED but also in improving dysuria caused by benign prostatic hyperplasia.
In addition, the Japanese Urological Association’s guidelines for the treatment of male lower urinary tract symptoms and benign prostatic hyperplasia report that tadalafil is an effective and safe treatment option for elderly patients.
2. Sildenafil (Viagra)
Sildenafil is one of the widely used PDE5 inhibitors for the treatment of ED (erectile dysfunction), with the well-known brand name Viagra. Sildenafil works by increasing blood flow to the penis and promoting erections, thereby supporting sexual activity. Below, we will provide detailed information about the mechanism of action, half-life, indications, and the perspective of the Japanese Urological Association. It is the only ED medication available over the counter in pharmacies.
1. Mechanism of Action
Sildenafil works by inhibiting the PDE5 (phosphodiesterase type 5) enzyme. PDE5 acts in the blood vessels of the penis, restricting blood flow. By suppressing the action of this enzyme, Sildenafil causes the smooth muscles in the penis to relax and increases blood flow, thereby promoting erections. However, sexual stimulation is necessary; taking the medication alone will not automatically result in an erection.
2. Half Life
The half-life of Sildenafil is approximately 4 to 5 hours. This affects the duration of the medication’s effects, which typically last for about 4 to 6 hours after administration. Due to its relatively short half-life, it is generally taken about one hour before sexual activity, allowing for the expected effects within a few hours.
This shorter half-life allows sildenafil to be taken when needed and to be eliminated from the body relatively quickly once its effects have ended. This is useful when the effects of the drug are not needed for long periods of time on a daily basis.
3. Diseases for which a particular medicine is indicated
Sildenafil is primarily used for the treatment of erectile dysfunction (ED). ED refers to the condition in which the penis does not achieve or maintain an adequate erection, making sexual activity difficult.
In addition, sildenafil has been used for other indications:
- Pulmonary Arterial Hypertension (PAH): Sildenafil is used to dilate the blood vessels in the lungs and lower blood pressure, making it effective for the treatment of PAH. It is prescribed under the brand name Revatio for this indication.
4. Dosage Instructions
Sildenafil is typically taken about one hour before sexual activity. It is affected by food intake, so taking it on an empty stomach can maximize its effectiveness. If taken after a meal, especially a high-fat meal, the absorption of the medication may be delayed, potentially leading to a slower onset of effects.
Onset of Action: Effects appear approximately 30 – 60 minutes after administration.
Duration of Action: Lasts approximately 4-5 hours.
A single dose is usually effective and one dose every 24 hours is recommended. If no effect is observed, it is important to consult a doctor and reconsider the appropriate dose and timing.
Medicines that should not be taken together
- Nitrates: Combined use with nitrates or nitric oxide-donating drugs used to treat chest pain can cause a sudden drop in blood pressure. These include nitroglycerin and isosorbide.
- Guanylate Cyclase Stimulants: Concomitant use with riociguat can also dangerously lower blood pressure and should be avoided.
- Certain Antibiotics and Antifungals: Including clarithromycin, erythromycin, ketoconazole and itraconazole, which may slow the breakdown of sildenafil in the body and may increase the risk of side effects.
- HIV Protease Inhibitors: concomitant use with HIV medicines such as ritonavir and saquinavir increases blood levels of sildenafil and increases the risk of side effects.
- Alpha-Blockers: when used in combination with telmisartan or doxazosin, which are used to treat hypertension and benign prostatic hypertrophy, they may intensify the blood pressure-lowering effect and cause dizziness and fainting spells.
5. Side Effect
Common side effects reported for sildenafil include:
- Headache
- Hot Face (Flushing)
- Indigestion
- Nasal Congestion
- Visual Disturbances (e.g. Bluish Vision)
These side effects are usually mild and temporary; however, in rare cases, serious side effects can occur. Particularly, if an erection lasts for more than four hours (known as priapism) or if there is a sudden loss of vision or hearing, it is important to consult a doctor immediately.
6. Contraindications and Precautions
There are several contraindications to the use of sildenafil. In particular, its use should be avoided in the following situations:
- Users of nitrate medications: Combining Sildenafil with nitrate medications used for treating conditions such as angina can lead to a sudden drop in blood pressure, which may be life-threatening.
- Patients with severe heart disease: Caution is necessary, as it may put additional strain on the heart.
7. Views of the Japanese Urological Association
The Japanese Urological Association recommends Sildenafil as one of the first-line options for the treatment of ED. PDE5 inhibitors demonstrate very high efficacy in treating ED, and Sildenafil is the most widely used medication among them.
The ED Treatment Guidelines provided by the Japanese Urological Association emphasize that the use of PDE5 inhibitors, including Sildenafil, is safe and effective for patients. It also highlights the need to carefully consider the effects of Sildenafil on other health conditions, such as cardiovascular diseases and diabetes. The guidelines recommend that medication therapy should be conducted alongside improvements in patients’ lifestyle habits and psychological support.
3. Vardenafil (Levitra)
Vardenafil is a PDE5 inhibitor that is widely used as a treatment for ED (erectile dysfunction). Well-known brand names include Levitra and Stendra. Like Sildenafil (Viagra) and Tadalafil (Cialis), Vardenafil increases blood flow to the penis to promote erections. Below, we will provide detailed information about Vardenafil’s mechanism of action, half-life, indications, and the perspective of the Japanese Urological Association.
1. Mechanism of Action
Vardenafil promotes erections by inhibiting the PDE5 (phosphodiesterase type 5) enzyme. PDE5 works in the blood vessels of the penis by breaking down cGMP (cyclic guanosine monophosphate), a substance that suppresses erections. By inhibiting PDE5, Vardenafil increases the concentration of cGMP, leading to vasodilation, increased blood flow, and relaxation of the smooth muscles in the penis.
However, vardenafil also requires sexual stimulation and an erection does not occur spontaneously just by taking the drug.
2. Half Life
The half-life of Vardenafil is approximately 4 to 5 hours. It has a similar short half-life to Sildenafil, with effects typically appearing within 30 minutes to 1 hour after ingestion and lasting for 4 to 6 hours. Therefore, Vardenafil is used as a medication that can be taken at the desired time, providing effects that conclude within a short duration.
This short half-life makes Vardenafil suitable for individuals who do not require prolonged erections but seek quick effects. Notably, Vardenafil is less affected by high-fat meals, meaning that taking it with food is less likely to delay its effectiveness.
3. Diseases for which a particular medicine is indicated
Vardenafil is primarily used for the treatment of erectile dysfunction (ED). It has been shown to be effective, especially for ED patients with conditions such as diabetes and cardiovascular diseases.
Additionally, Vardenafil can be used for the treatment of pulmonary arterial hypertension (PAH), similar to Sildenafil. However, other PDE5 inhibitors are more commonly used for this indication.
4. Dosage Instructions
Vardenafil is typically taken about one hour before sexual activity. The onset of effects can vary between individuals but usually occurs within about 30 minutes, lasting up to 4 to 6 hours. Another advantage of Vardenafil is its reduced sensitivity to food intake; even after a high-fat meal, it is less likely to experience delays in effectiveness compared to Sildenafil, allowing for more flexible timing around meals.
It should not be taken more than once a day, and even if it does not work, it should be taken again after 24 hours.
It is less affected by diet, but alcohol and oily food may weaken its effect.
Medicines that should not be taken together
- Nitrates: Concomitant use with nitrates such as nitroglycerin and isosorbide mononitrate can cause a dangerous drop in blood pressure.
- Guanylate Cyclase Stimulants: E.g. riociguat may cause extreme reductions in blood pressure and should not be used in combination.
- Strong Inhibitors of CYP3A4: Some HIV protease inhibitors (e.g. ritonavir, indinavir), antifungals (e.g. ketoconazole, itraconazole) and antibiotics (e.g. clarithromycin) increase the blood levels of vardenafil and increase the risk of side effects.
- Alpha-Blockers: Concomitant use with drugs used to treat hypertension and prostate enlargement (e.g. alfuzosin, doxazosin) may risk lowering blood pressure too much.
Actions to Avoid
- Heavy Alcohol Consumption: Alcohol is a vasodilator and may cause an excessive drop in blood pressure when taken with vardenafil.
- Machinery Operation: caution should be exercised when driving or operating machinery as vardenafil can affect vision.
5. Side Effect
Common side effects of vardenafil include the following:
- Headaches
- Hot Face
- Nasal Congestion
- Indigestion
- Eye Redness
These side effects are generally mild and temporary, but serious side effects can occasionally occur. In particular, if priapism (an erection lasting more than four hours) or sudden loss of vision or hearing occurs, immediate medical attention is required.
6. Contraindications and Precautions
There are several contraindications to the use of vardenafil, restricting its use to certain patients:
- Users of Nitrate Medications: If you are taking nitrates for conditions such as angina, the use of Vardenafil is contraindicated, as it may cause a sudden drop in blood pressure.
- Patients with Severe Heart Disease: Those with a history of heart disease should consult a doctor, as Vardenafil may put additional strain on the heart.
Careful use is also recommended in patients with impaired kidney or liver function and in the elderly.
7. Opinion of the Japanese Urological Association
The Japanese Urological Association recommends Vardenafil as a treatment option for ED. Overall, PDE5 inhibitors have been confirmed to be effective and safe for treating ED, and Vardenafil is one of them. Notably, Vardenafil is often considered easier to use than Sildenafil due to its reduced sensitivity to food intake.
The ED Treatment Guidelines from the Japanese Urological Association recommend Sildenafil, Vardenafil, and Tadalafil as first-line options. The optimal medication is chosen based on the patient’s lifestyle and health conditions. These medications are considered safe for use, even in patients with underlying conditions such as diabetes and hypertension.
Selection of Each Drug
- Selection Criteria: When starting treatment, it is essential to consider factors such as duration of action, ease of use, degree of side effects, individual health conditions, and potential interactions with other medications.
- Side Effects: Common side effects include headache, facial flushing, indigestion, and nasal congestion. However, serious side effects (e.g., vision impairment, hearing loss, prolonged erections) may also occur, so caution is necessary.
- Medical Advice: It is essential to seek a doctor’s diagnosis and advice when starting ED treatment. A physician can recommend the most suitable medication based on the patient’s health condition and lifestyle.
Each of these drugs has its own advantages and caveats, so it is important to discuss these with your Hiro Clinic doctor to make the best choice for you.
