Cialis (Tadalafil): Effects, Side Effects, Dosage & How to Take | Physician-Supervised Guide

The active ingredient in Cialis^®, tadalafil, selectively inhibits the PDE5 (phosphodiesterase type 5) enzyme in the corpus cavernosum of the penis. PDE5 is the enzyme responsible for breaking down cGMP (cyclic guanosine monophosphate). When sexual stimulation triggers the release of nitric oxide (NO), cGMP levels increase, causing smooth muscle relaxation and vasodilation. By suppressing PDE5, tadalafil prolongs elevated cGMP levels, increasing blood flow to the penis and facilitating erection.

It is important to note that tadalafil does not cause an automatic erection without sexual stimulation. It is a medication that assists the erectile mechanism, and psychological arousal and partner interaction remain essential prerequisites.

According to IMS Health data, tadalafil (Cialis^®) holds the No. 1 market share among ED medications worldwide. The two key reasons are its duration of action lasting up to 36 hours and its minimal sensitivity to food and alcohol intake. While sildenafil (Viagra^®) lasts 4–6 hours and vardenafil (Levitra^®) lasts 4–8 hours, tadalafil’s 36-hour duration far surpasses both.

Taking one tablet on Saturday evening means the effects can last through Sunday afternoon. This eliminates the psychological pressure of wondering when to schedule intimacy, significantly reducing the anxiety and stress associated with ED. This is precisely why it earned the name “Weekend Pill.”

Since the Cialis^® patent expired around 2016, numerous generic versions have become available both domestically and internationally. In Japan, notable generics include Sawai Pharmaceutical’s “Tadalafil Tablets CI ‘SAWAI'” and Towa Pharmaceutical’s “Tadalafil OD Tablets CI ‘TOWA’.”

Many patients search for the differences between branded Cialis^® and generic tadalafil, but the answer is straightforward: the active ingredient, efficacy, and duration of action are exactly the same. The only differences are tablet appearance, inactive ingredients, and price. Generics are typically 30–50% less expensive than the branded version, making them a more cost-effective choice for long-term use.

Men’s Care Clinic carries both branded Cialis^® and domestically approved generic tadalafil. During your initial visit, a physician will recommend the best option based on your lifestyle and budget.

The estimated time from administration to onset of action is 30 minutes to 2 hours. However, there is considerable individual variation depending on metabolic rate, fasting state, and psychological condition. If you are taking tadalafil for the first time, using the guideline of “take it 1 hour beforehand” is recommended.

• 30 minutes to 1 hour: Most patients begin to notice effects
• 1 to 2 hours: Plasma concentration approaches peak levels; this is the most stable period of efficacy
• Up to 36 hours: Effective concentrations are maintained (individual variation applies)

While sildenafil (Viagra^®) requires strict timing of “30 minutes before intercourse,” tadalafil offers a much wider dosing window, making it well-suited for those who find it difficult to plan sexual activity in advance.

The defining feature of tadalafil (Cialis^®) is its duration of action of up to 36 hours, attributable to tadalafil’s long elimination half-life (approximately 17.5 hours). A longer half-life means the drug is metabolized slowly within the body, resulting in prolonged efficacy.

However, this does not mean you will have an erection lasting 36 hours. The accurate understanding is that “for up to 36 hours, your body remains more responsive to sexual stimulation.” Without sexual arousal, you will remain in a natural, non-erect state.

Tadalafil (Cialis^®) is available in three dosage strengths: 5 mg, 10 mg, and 20 mg. For first-time users, starting with 10 mg is standard practice.

The difference between tadalafil 10 mg and 20 mg is straightforward: the higher dose tends to produce stronger effects but also increases the likelihood of side effects (headache, flushing, etc.). The recommended approach is to try 10 mg first and increase to 20 mg only if the effect is inadequate.

The tadalafil 5 mg once-daily regimen involves taking a low dose at the same time each day to maintain a consistent plasma concentration. Compared to as-needed dosing (10 mg or 20 mg), this approach offers the following advantages:

• No need to time sexual activity at all: Effective plasma concentrations are maintained continuously
• Fewer side effects: The low dose results in a more gradual increase in plasma concentration per dose
• Improvement in erectile function: Evidence shows that continuous daily use can improve erectile function itself over time

The drawbacks are the need to establish a daily medication habit and the ongoing monthly cost. Men’s Care Clinic offers pay-per-visit pricing starting from a single tablet, so you can begin with as-needed dosing and switch to daily use whenever you decide you want a more effortless approach.

The most frequently reported side effects of tadalafil (Cialis^®) are listed below. These are related to vasodilation and typically resolve spontaneously within a few hours.

A particularly characteristic side effect of tadalafil is back pain and myalgia. Rarely seen with sildenafil (Viagra^®) or vardenafil (Levitra^®), this may manifest as stiffness in the lower back or back muscles 12–24 hours after administration. It typically resolves within 48 hours.

Concerns about tadalafil (Cialis^®) causing hair loss are frequently searched online. Based on current medical evidence, there is no clear proof that tadalafil causes hair loss or increased hair shedding.

The prescribing information for tadalafil does not list “alopecia” or “hair loss” among its documented adverse effects. Tadalafil is a PDE5 inhibitor, and its mechanism of action is entirely different from that of DHT (dihydrotestosterone), the causative substance of androgenetic alopecia (AGA).

However, both ED and AGA become more common in men over 40–50, so it is understandable that some patients suspect a connection when AGA progression coincides with starting tadalafil. This is considered a temporal coincidence rather than a causal relationship.

Another common concern is whether tadalafil directly causes baldness. The conclusion is that there is currently no evidence that tadalafil (Cialis^®) directly causes hair thinning or baldness.

The primary cause of AGA is DHT, a male hormone that miniaturizes hair follicles. Tadalafil acts selectively on the PDE5 enzyme and does not affect 5-alpha reductase, the enzyme that converts testosterone to DHT. Therefore, there is no pharmacological mechanism by which it would promote AGA.

If you feel that your hair has become thinner since starting tadalafil, it is highly likely that natural AGA progression coincidentally overlapped with the timing of treatment. If this concerns you, Men’s Care Clinic also offers specialized AGA consultations.

Conversely, some people search for whether tadalafil can promote hair growth. This speculation likely stems from tadalafil’s vasodilatory properties and the assumption that improved scalp blood flow might stimulate hair growth.

At present, there is insufficient evidence to support the claim that tadalafil is effective for hair growth or hair regrowth. While some research has reported increased PGE2 (prostaglandin E2) secretion in dermal papilla cells, this has not yet been established as a clinically significant hair growth effect.

If hair growth is your goal, we recommend consulting a specialist about established AGA treatments such as minoxidil, finasteride, or dutasteride. Through Men’s Care Clinic’s partnership with Toyosu Hospital (Showa University affiliate), it is possible to receive both ED treatment and AGA treatment simultaneously.

Many patients search for information about tadalafil and blindness. To state the conclusion upfront: a direct causal relationship between tadalafil use and blindness has not been established, although reports of visual disturbances do exist.

Specifically, mild visual changes such as “increased sensitivity to light” and “temporary color vision changes (a bluish tint)” have been reported. These are attributed to weak inhibition of PDE6 (phosphodiesterase present in the retina) and are temporary.

However, a very rare but serious adverse event called non-arteritic anterior ischemic optic neuropathy (NAION)—a disruption of blood flow to the optic nerve—has been reported. Cases have been documented primarily in higher-risk populations such as those with low ocular perfusion pressure or cardiovascular disease; the incidence in generally healthy individuals is extremely low.

If you experience sudden vision loss or visual impairment after taking the medication, discontinue use immediately and seek medical attention. If you have concerns, we encourage you to consult a physician beforehand. Men’s Care Clinic also offers convenient online consultations.

Below are key strategies for minimizing the side effects of tadalafil (Cialis^®):

• Start with 10 mg for your first dose: Beginning with 20 mg may produce stronger side effects. Assess your response at 10 mg first
• Limit alcohol consumption: Combining alcohol with tadalafil increases the risk of hypotension (details below)
• Avoid grapefruit: Grapefruit inhibits the metabolic enzyme CYP3A4, potentially causing tadalafil plasma concentrations to rise beyond expected levels
• Stay well hydrated: Effective for preventing headaches. Drink 1–2 glasses of water before and after administration
• Avoid vigorous exercise immediately after dosing: To prevent blood pressure fluctuations, rest for approximately 30 minutes after taking the medication
• Consider switching to daily low-dose (5 mg): For patients who experience side effects with as-needed dosing, switching to a once-daily regimen may provide improvement

If side effects are a concern, do not discontinue on your own—consult a physician at Men’s Care Clinic instead. We are available at our Shimbashi, Akihabara, and Omotesando locations, as well as through online consultations.

A common question is whether tadalafil should be taken before or after meals. The answer: tadalafil (Cialis^®) can be taken with or without food.

Unlike sildenafil (Viagra^®), whose absorption is significantly delayed by high-fat meals, clinical trials have confirmed that tadalafil is minimally affected by food. Even after a high-fat meal, the maximum plasma concentration (C_max) and time to peak concentration (T_max) remain virtually unchanged.

That said, taking tadalafil 30–60 minutes after a meal is generally recommended. For those prone to gastrointestinal side effects (heartburn, dyspepsia), having food in the stomach at the time of dosing may help alleviate symptoms.

The one exception to be aware of is grapefruit (and grapefruit juice). Furanocoumarins in grapefruit inhibit the hepatic metabolic enzyme CYP3A4, potentially causing tadalafil plasma concentrations to rise unexpectedly high. This increases the risk of side effects, so avoid grapefruit on the day you take the medication.

Regarding alcohol and tadalafil: while small amounts are not necessarily contraindicated, caution is required. Both tadalafil and alcohol lower blood pressure, so combining them may cause an excessive drop in blood pressure.

• Small amounts (1–2 beers): Risk is relatively low, but monitor your condition carefully
• Moderate or more (equivalent to 2+ glasses of wine): Hypotension, dizziness, and headache may intensify. Avoidance is recommended
• Heavy drinking: Worsens erectile dysfunction (alcohol itself causes ED) and amplifies tadalafil side effects. Absolutely avoid

Alcohol also directly impairs erectile function. Using tadalafil after heavy drinking is the worst-case scenario: the medication becomes less effective while the risks increase. We recommend taking tadalafil with minimal or no alcohol consumption.

Regarding drug interactions and contraindications for tadalafil (Cialis^®), the following medications require particular caution:

Patients taking nitrates (medications for angina) must not use tadalafil. If you are concerned about blood pressure effects or are taking multiple medications, always inform your physician before starting treatment. At Men’s Care Clinic, all current medications are reviewed during the consultation before prescribing.

The concept of vascular rejuvenation with tadalafil is scientifically well-founded, referring to tadalafil’s ability to improve vascular endothelial function. The vascular endothelium is a critical tissue that regulates blood flow, and its age-related decline is a fundamental contributor to atherosclerosis and cardiovascular disease.

Multiple clinical studies have confirmed that continuous tadalafil use improves flow-mediated dilation (FMD), a measure of vascular elasticity and endothelial function. Higher FMD values indicate a “younger vascular age.” In other words, regular tadalafil use may contribute to vascular rejuvenation.

Regarding tadalafil and testosterone: rather than directly stimulating testosterone production, the proposed mechanism involves improved blood flow supporting testicular function. Since ED is often associated with low testosterone, improving ED may help restore a healthier hormonal balance.

What happens with daily tadalafil use? This is an important question. Large-scale clinical trials (including the REFRACT trial, published in 2011) demonstrated that daily 5 mg tadalafil significantly improves erectile function compared to as-needed dosing.

The following benefits of daily low-dose administration have been reported:

• Sustained improvement in erectile function scores (IIEF): A “carry-over effect” has been observed, with benefits persisting even after discontinuation
• Prevention of corpus cavernosum fibrosis: Prevents degenerative changes (aging) of the cavernous tissue that occur with disuse
• Increased nocturnal penile tumescence (NPT): Nocturnal erections are critical for oxygen delivery to penile tissue; their increase helps maintain tissue health
• Improvement of benign prostatic hyperplasia (BPH): Tadalafil also improves blood flow to the prostate and bladder, with confirmed benefits for urinary difficulties caused by BPH

In summary, daily tadalafil use extends beyond simple ED treatment to encompass maintenance and rejuvenation of male sexual function. Men’s Care Clinic incorporates the latest evidence to recommend the optimal regimen and dosage for each individual patient.

Among the three PDE5 inhibitors, tadalafil (Cialis^®) offers the greatest flexibility in timing. Being able to take it even after a dinner out is a significant advantage of tadalafil’s low food sensitivity. On the other hand, sildenafil (Viagra^®) remains a strong choice for those who prioritize rapid onset or cost savings (many generics are available).

Vardenafil (Levitra^®) has the fastest onset at 15–30 minutes, but since the branded product’s marketing authorization was withdrawn in 2021, only generic versions are currently available. It tends to be more expensive than tadalafil or sildenafil generics.

Some patients ask about combining ED medications. The answer: concurrent use of multiple ED medications is generally not practiced.

Since sildenafil (Viagra^®), vardenafil (Levitra^®), and tadalafil (Cialis^®) are all PDE5 inhibitors, taking two simultaneously does not double the effect; rather, it increases the risk of side effects such as hypotension, headache, and flushing. Additionally, because tadalafil has such a long duration of action, taking a different ED medication the day after tadalafil is also potentially dangerous.

If you feel the current medication is not working well enough, the appropriate approach is to either switch to a different medication or adjust the dosage of your current one in consultation with your physician. Men’s Care Clinic’s experienced physicians will help determine the optimal prescription for you.

Prices differ significantly between branded Cialis^® and generic tadalafil. Men’s Care Clinic offers pay-per-visit pricing starting from a single tablet—no package contracts required.

*The above are estimated prices. Consultation fees and shipping charges may apply separately. Please contact the clinic for the latest pricing.

Regarding insurance coverage for tadalafil: as a general rule, prescriptions for ED treatment are not covered by insurance (self-pay only).

However, there are exceptions. For organic ED resulting from post-prostatectomy or spinal cord injury, sildenafil (generic Viagra^®) may be covered by insurance. As for tadalafil, it is covered by insurance under the brand name “Zalutia” for the treatment of urinary difficulties caused by benign prostatic hyperplasia (BPH)—though this is as a BPH treatment, not as an ED treatment.

Prescriptions as part of infertility treatment are also generally not covered by insurance. If you have questions about whether insurance applies in your case, please consult with a physician at Men’s Care Clinic.

Tadalafil use in patients aged 65 and older is not contraindicated, but requires cautious administration. Elderly patients often have reduced renal and hepatic function, which can slow the metabolism and elimination of tadalafil. As a result, the same dose may produce higher plasma concentrations and increase the likelihood of side effects.

• Patients aged 65+: Start with 5 mg and assess efficacy and tolerability before considering dose escalation
• Patients with cardiovascular disease or hypertension: Use only after clearance from the treating physician. Monitor for interactions with antihypertensive medications
• Patients with hepatic or renal impairment: Dose adjustment is required based on severity. Always disclose this to your physician
• Patients undergoing prostate cancer treatment: Verify potential interactions with endocrine therapy (hormone therapy) with your physician

Through its partnership with Toyosu Hospital (Showa University affiliate), Men’s Care Clinic has a comprehensive support system for patients with underlying conditions. We welcome consultations from patients managing multiple health issues.

• Those who don’t want to worry about timing: The 36-hour duration eliminates the need to plan sexual activity. Ideal for weekends or business trips
• Those who dine out frequently: Minimal impact from high-fat meals means it can be taken even right before dinner
• Those who prefer milder side effects: The daily 5 mg regimen produces lower per-dose plasma concentration peaks, reducing the likelihood of side effects
• Those interested in anti-aging: Long-term benefits including vascular rejuvenation, testosterone maintenance, and improved erectile function
• First-time ED medication users: No food restrictions and wide dosing flexibility make it easy to use from the very first time

Men’s Care Clinic operates three locations: Shimbashi, Akihabara, and Omotesando. Through our partnership with Toyosu Hospital (Showa University affiliate), we provide a safe and supportive environment for patients with underlying conditions or advanced age.

• Pay-per-visit, single-tablet prescriptions: No package contracts required. Walk in even if you just want to try it once
• Physician-supervised, in-house dispensing: Your attending physician handles everything from consultation to prescription. Guaranteed authentic, domestically approved products
• Online consultation available: For those who cannot visit in person, video consultations with same-day prescription and home delivery are available
• First-time offer: Online consultation only—10 generic tadalafil tablets for 5,000 yen (limited quantities and duration)

If you are interested in trying tadalafil (Cialis^®) or switching from your current medication, please do not hesitate to contact Men’s Care Clinic.