Action and Spectrum

Actions and Spectrum: 

The actions of tadalafil include: 

• Relaxation of the smooth muscles in the walls of blood vessels leads to increased blood flow to the penis and lungs. 
• Inhibition of the PDE5 enzyme, which prevents the breakdown of cyclic guanosine monophosphate (cGMP), a chemical responsible for relaxing smooth muscles. 
• Enhancement of the effects of nitric oxide, a natural chemical involved in relaxing blood vessels. 

The spectrum of tadalafil primarily focuses on its use in treating ED and PAH. In the ED, tadalafil effectively improves the ability to achieve and maintain an erection during sexual stimulation. For PAH, tadalafil can improve exercise capacity and reduce the risk of clinical worsening. 

Drug Interaction

Adverse Reaction

Frequency defined 

>10% 

Headache  

Myalgia  

Respiratory tract infection  

Nasopharyngitis  

Dyspepsia  

Flushing  

Back pain  

Nausea  

1-10% 

Nasal congestion  

Gastroesophageal reflux disease  

Hypertension  

Bronchitis  

Genitourinary tract infection  

<1% 

Amnesia 

Angina pectoris 

Arthralgia 

Change in color vision 

Conjunctival hyperemia 

Dyspnea 

Epistaxis 

Black Box Warning

Contraindication / Caution

Contraindication/Caution: 

tadalafil is a relatively safe medication, but there are some situations in which its use may be contraindicated or require caution. These include: 

• Allergy or hypersensitivity to tadalafil or any of its components. 
• Use of nitrates or nitric oxide donors (such as amyl nitrate or nitroglycerin) for the treatment of chest pain or heart problems, as this combination can cause a dangerous drop in blood pressure. 
• Use of alpha-blockers for the treatment of high blood pressure or prostate problems, as these medications can also cause a drop in blood pressure when taken with tadalafil. 
• Severe liver or kidney disease, as tadalafil is metabolized by the liver and excreted by the kidneys. 
• History of vision loss or certain eye conditions (such as non-arteritic anterior ischemic optic neuropathy) that affect blood flow to the optic nerve. 
• History of heart attack or stroke within the past 6 months. 
• Use of recreational drugs, such as poppers (amyl nitrate or butyl nitrate), which can also cause a dangerous drop in blood pressure when taken with tadalafil. 

Caution should also be used in individuals with: 

• Low blood pressure or uncontrolled high blood pressure. 
• Diabetes or other conditions that affect blood vessels. 
• History of priapism (a painful, prolonged erection). 
• Bleeding disorders or taking blood thinners. 
• Anatomical deformation of the penis or predisposition to priapism. 
• Severe hearing or vision problems. 

Pregnancy / Lactation

Pregnancy consideration:  

Not recommended to be used in pregnant women 

Breastfeeding warnings:  

The drug is excreted in breastmilk 

Pregnancy category: 

• Category A: Satisfactory and well-controlled studies show no risk to the fetus in the first or later trimester. 
• Category B: No evidence shown of risk to the fetus found in animal reproduction studies, and there are not enough studies on pregnant women    
• Category C: Adverse effects on the fetus found with evidence in animal reproduction studies and no adequate evidence for a product in humans; Pregnant women must take care of the potential risks. 
• Category D: There is adequate data available with sufficient evidence of human fetal risk from various platforms. However, despite potential dangers may be used only in emergency cases for potential benefits. 
• Category X: Drugs listed in this category outweigh risks over benefits. The drug is not for pregnant women. 
• Category N: No data is available for the drug under this category. 

Pharmacology

Pharmacology: 

tadalafil is a medication used to treat erectile dysfunction (ED) and pulmonary arterial hypertension (PAH). It belongs to the class of drugs called phosphodiesterase type 5 (PDE5) inhibitors. 

tadalafil works by inhibiting the enzyme PDE5, which is responsible for cyclic guanosine monophosphate (cGMP) degradation. cGMP is a molecule that causes the smooth muscle cells in the penis to relax, allowing for increased blood flow and erection. By inhibiting PDE5, tadalafil increases cGMP levels, leading to improved erectile function. 

In addition to its effects on erectile function, tadalafil relaxes the smooth muscle cells in the pulmonary arteries, leading to decreased pulmonary arterial resistance and improved exercise capacity in patients with PAH. 

tadalafil is absorbed rapidly after oral administration, with peak plasma concentrations occurring within 2 hours. It has a half-life of approximately 17.5 hours, meaning it remains in the body for a prolonged period. tadalafil is metabolized by the liver and excreted in the feces and urine. 

Pharmacodynamics: 

tadalafil is a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5), an enzyme responsible for the degradation of cGMP in the corpus cavernosum of the penis. By inhibiting PDE5, tadalafil increases the cGMP concentration, leading to smooth muscle relaxation, vasodilation, and increased blood flow to the penis. This results in improved erectile function in men with ED. 

Pharmacokinetics: 

Absorption 

Duration of action ≤36 hour 

Peak plasma time: Erectile dysfunction, 0.5-6 hr; PAH, 2-8 hr 

Distribution 

The protein-bound is 94% 

The volume of distribution in the case of erectile dysfunction is 63 L, and for PAH is 77 L 

Metabolism 

The drug is metabolized in liver by CYP3A4 

Elimination and Excretion 

The half-life for erectile dysfunction is 15-17.5 hour; and for PAH is 35 hours 

Total body clearance: Erectile dysfunction, 2.5 L/hr; PAH (not on bosentan), 1.6 L/hr 

The drug is excreted 61% in feces and 36% in urine

Adminstartion

Administration: 

tadalafil is a medication used to treat erectile dysfunction (ED) and benign prostatic hyperplasia (BPH) symptoms. It works by relaxing the blood vessels and increasing blood flow to the penis, allowing for a sustained erection. 

Tadalafil is usually taken orally, with or without food, as directed by a healthcare provider. The medication is available in different strengths, and the appropriate dose depends on the individual’s needs and medical condition. 

It is essential to follow the dosage instructions carefully and not exceed the recommended dose. Tadalafil should not be taken more than once per day. It may take several hours for the medication to take effect, so it is recommended to take it at least 30 minutes before sexual activity. 

Patient Information Leaflet

Patient information leaflet 

Generic Name: tadalafil 

Pronounced: ta-DAL-a-fil 

Why do we use tadalafil? 

tadalafil is primarily used to treat two conditions: 

• Erectile dysfunction (ED): ED is a common condition in which a man has difficulty achieving or maintaining an erection during sexual activity. Tadalafil increases blood flow to the penis, helping achieve and maintain an erection. 
• Benign prostatic hyperplasia (BPH): BPH is a noncancerous prostate gland enlargement that can cause urinary problems, such as difficulty urinating or frequent urination. Tadalafil can help improve the symptoms of BPH by relaxing the muscles in the prostate and bladder, allowing for easier urination.