Overview
Cialis is tracked as a supplement in Milligram's compound library. Phosphodiesterase type 5 inhibitor.
With a half-life of ~17.5 hours, Cialis requires daily administration in most observed protocols. Taken orally, it has a bioavailability of approximately 95% via its primary route.
Half-life approximately 17.5 hours — longest in its class. Duration of pharmacological activity extends to approximately 36 hours. One-compartment model.
Mechanism of Action
Cialis's pharmacological activity involves the following key pathways:
Primary Mechanism
Cialis exerts its effects through its established pharmacological pathway. Its mechanism has been characterized in published research.
Enzyme Modulation
Cialis modulates specific enzymatic pathways relevant to its pharmacological effects.
Dosing Protocols
The following protocols represent commonly observed dosing patterns. These are observational summaries, not recommendations.
Dose
2.5 mg/day
Route
Oral
Frequency
Once daily
Duration
Ongoing
Dose
10 mg/day
Route
Oral
Frequency
Once daily
Duration
Ongoing
Frequently Asked Questions
What is tadalafil (Cialis) and how does it work?
Tadalafil is a PDE5 (phosphodiesterase type 5) inhibitor that increases blood flow to smooth muscle tissue by preventing the breakdown of cyclic GMP (cGMP). This mechanism produces vasodilation, most notably in penile and pulmonary vascular tissue. It is FDA-approved for erectile dysfunction, benign prostatic hyperplasia, and pulmonary arterial hypertension, and its long 17.5-hour half-life distinguishes it from other PDE5 inhibitors like sildenafil.
What is the difference between daily low-dose tadalafil and as-needed dosing?
Daily low-dose tadalafil (2.5–5 mg/day) maintains consistently elevated cGMP levels around the clock, allowing spontaneous erectile response without timing a dose to sexual activity. As-needed dosing (10–20 mg taken 30–60 minutes before activity) provides a larger concentration spike for acute use. Daily dosing is also associated with additional cardiovascular and BPH benefits beyond on-demand erectile function.
What are the potential benefits of low-dose daily tadalafil beyond erectile dysfunction?
Daily tadalafil at 2.5–5 mg has been studied for BPH symptom relief, improved endothelial function, and modest cardiovascular benefits including reduced arterial stiffness. There is emerging interest in its use alongside testosterone replacement therapy, where it may support erectile function, exercise capacity, and vascular health. Some research suggests PDE5 inhibition may have favorable effects on metabolic markers including insulin sensitivity.
What are the common side effects of tadalafil?
The most commonly reported side effects are headache, flushing, nasal congestion, indigestion, and back pain or muscle aches – the latter being more specific to tadalafil than other PDE5 inhibitors and attributed to PDE11 inhibition. These effects are generally dose-dependent and transient. Tadalafil is contraindicated with nitrate medications due to the risk of severe hypotension.
Can tadalafil be used with testosterone or peptides?
Tadalafil is commonly used alongside testosterone replacement therapy, where it supports vascular function and erectile response that may be impaired during TRT initiation. It is also used in stacks with PT-141 (bremelanotide) for a complementary peripheral (vascular) and central (melanocortin) approach to sexual function. No significant pharmacokinetic interactions have been reported between tadalafil and common peptides.
How long does tadalafil stay active in the body?
With a half-life of approximately 17.5 hours, a single dose of tadalafil remains pharmacologically active for up to 36 hours – earning it the nickname 'the weekend pill.' Steady state on a daily dosing schedule is reached within approximately 4 days. The extended duration is what distinguishes tadalafil from sildenafil (4–6 hour half-life) and makes it suitable for both daily and as-needed protocols.