Warnings and precautions
Patients currently taking nitrates, experiencing angina pectoris, suffering from heart disease, patients who have unregulated hypertension or hypotension, or patients who have had a stroke in the past 6 months should not take Cialis.
Adverse effects related to oral therapy for erectile function are primarily concerned with adverse cardiovascular effects, because PDE5
inhibitors promote vasodilation and, therefore, have an inherent potential to cause hypotension. This is a particular concern for elderly
patients with a preexisting condition.
Tadalafil (market name “Cialis” or “Adcirca”) is a kind of PDE5 inhibitor used for the treatment of erectile dysfunction, benign prostatic hypertrophy and pulmonary arterial hypertension. The effect of Tadalafil is relaxing the blood vessels muscles and increasing the blood flow into the corpus cavernosum. The mechanism of action of tadalafil is through inhibiting the activity of the cGMP specific phosphodiesterase type 5 (PDE5). PDE5 degrades cGMP in the corpus cavernosum located around the penis. Therefore, tadalafi leads to the increased concentration of cGMP which further causes the smooth muscle relaxation and increased blood flow into the corpus cavernosum. Some clinical studies also implied that tadalafil could improve endothelia function in men with increased cardiovascular risk and lower the urinary tract symptoms secondary to benign prostatic hyperplasia.
analgesic, norepinephrine uptake blocker, mu-opiod receptor agonist.A phosphodiesterase 5 inhibitor.
D-(-)-Tryptophan methyl ester (175) and 1,3-
benzodioxole-5-carboxaldehyde (176) were subjected to a
modified Pictet-Spengler reaction to form cis- and transtetrahydro-
β-carboline tricyclic compounds. The ciscompound
177 was isolated as a white solid in 42% yield.
The basic nitrogen in the piperidine ring of 177 was acylated
with chloroacetyl chloride (179) to give compound 180 in
93% yield. Finally, the diketonepiperazine ring was formed
by adding 180 to 33% methylamine in ethanol under
refluxing conditions and yielded tadalafil (XXII) in 77% as
a white solid.
Tadalafil is different in structure from both sildenafil and vardenafil. It is rapidly absorbed and peaks in concentration (378 μg/L after a
20-mg dose) after 2 hours, displaying a long half-life of 17.5 hours. It also is metabolized by the liver (CYP3A4). Notably, its
pharmacokinetics is not clinically influenced by alcohol or food intake or by factors such as diabetes or impaired hepatic or renal
Roehrborn, C. G., et al. "Tadalafil administered once daily for lower urinary tract symptoms secondary to benign prostatic hyperplasia: a dose finding study." Journal of Urology 180.4(2008):1228.
Rosano, Giuseppe M. C., et al. "Chronic Treatment with Tadalafil Improves Endothelial Function in Men with Increased Cardiovascular Risk." European Urology 47.2(2005):214-222.
Tadalafil is one of the two new PDE5 inhibitors launched for the oral
treatment of male erectile dysfunction. Tadalafil is a b-carboline derivative and it is
structurally distinct from vardenafil (Levitraw) and sildenafil (Viagraw), both of
which are PDE5 inhibitors based on a fused pyrimidine core structure. Tadalafil is
synthesized in three steps starting from D-tryptophan methyl ester, by first
condensing with piperonal in a Pictet-Spengler cyclization reaction to form the
tetrahydro-β-carboline derivative, which is followed by chloroacetylation of the
piperidine ring nitrogen and cyclization with methylamine. Tadalafil is a potent and
highly selective inhibitor of PDE5 (IC50=1 nm). It shows ＞10,000-fold selectivity
for PDE5 versus PDE1, 2, 3, 4, 7, 8 and 9, and ＞700-fold selectivity versus PDE6.
Typically administered at 10 and 20 mg doses, tadalafil is rapidly absorbed and has a
tmax of 2 h, which is slightly longer than those of sildenafil (1 h) and vardenafil
(0.75 h). Clinically, all of these agents appear to have efficacy for many men within
30–60 min. However, tadalafil distinguishes itself from other PDE5 inhibitors in
terms of significantly longer duration of action. The half-life of tadalafil dosed at
20 mg is 17.5 h as compared with 3.8 h for sildenafil (100 mg) and 4.7 h for
vardenafil (20 mg). In clinical studies, significant rates of response were reported up
to 36 h following drug ingestion. Tadalafil is predominantly metabolized in the liver
by CYP3A4 to entities that are not active against PDE5 and excreted mainly as
metabolites in the feces and the urine. The pharmacokinetics of tadalafil are
unaffected by factors such as intake of food and alcohol, age, the presence of
diabetes, and mild or moderate hepatic insufficiency. The most common drug-related
adverse events are headache, back pain, dyspepsia, and myalgia. At 10 and 20 mg
doses, Tadalafil does not have a significant effect on blood pressure and heart rate
and does not result in increased instances of myocardial infarction. Rare reports of
prolonged erections greater than 4 h and priapism have been noted with the use of
tadalafil. Priapism, if not treated properly, can result in irreversible damage to the
erectile tissue. Patients who have an erection lasting greater than 4 h are advised
to seek emergency medical attention. Tadalafil has a modest synergistic effect on the nitrate-induced reduction in blood pressure and, as with sildenafil and
vardenafil, it is contraindicated for use in patients on nitrate therapy. In diabetic
patients, improvement of erectile function by tadalafil is irrespective of the type of
diabetes and the type of diabetic therapy.
Indications and uses
Cialis (or Tadalafil) was developed by American pharmaceutical company Lilly. It is used to treat erectile dysfunction and belongs to a second generation of PDE5 inhibitors. Studies show that Cialis works very quickly, taking effect in around 15-20 minutes, and has a prolonged effect that can last for up to 36 hours. T1/2 is 17.5h.
White to Off-White Cyrstalline Solid
ChEBI: A pyrazinopyridoindole that is 2,3,6,7,12,12a-hexahydropyrazino[1',2':1,6]pyrido[3,4-b]indole-1,4-dione substituted at position 2 by a methyl group and at position 6 by a 1,3-benzodioxol-5-yl group (the 6R,12aR
Mechanism of action
Tadalafil was the last agent to be released and can be taken on a full stomach without slowing the onset. It has a much longer duration of action, lasting up to 48 hours, compared with sildenafil and vardenafil, which last for approximately 4 hours. The longer half-life of tadalafil results in a lengthened period of responsiveness as compared to sildenafil and vardenafil. This longer therapeutic window requires fewer time constraints for the effectiveness of tadalafil and has been interpreted as being advantageous through providing the option for more spontaneous sexual activity. Because of its long half-life, however, tadalafil, has been detected in plasma even 5 days after oral administration. This suggests the possibility of accumulation if taken regularly and in short intervals, which may result in an increased risk of side effects with the excessive use of this PDE5 inhibitor. The 3,4-methylenedioxy substitution on the phenyl ring was significant for increasing its potency as PDE5 inhibitor. Optimization of the chain on the piperazinedione ring resulted in no significant change in IC50s. Tadalafil is a highly potent PDE5 inhibitor (IC50, 5 nM), with high selectivity for PDE5 versus PDE1 through PDE4. The PDE5/PDE6 selectivity ratio is 85.
Tadalafil, (6R-trans)-6-(1,3-benzodioxol-5-yl)-2,3,6,7,12,12a-hexahydro-2-methyl-pyrazino[1＇, 2＇ :1,6]pyrido[3,4-b]indole-1,4-dione (Cialis), is a potent PDE5 inhibitor.It received FDA approval for the treatment of erectiledysfunction in December 2003. Because of its half-life of17.5 hours, it is marketed as a 36-hour treatment. Tadalafil ispredominantly metabolized by hepatic enzymes, includingCYP3A4. The concomitant use of CYP3A4 inhibitors suchas ritonavir, indinavir, ketoconazole, as well as moderateCYP3A inhibitors such as erythromycin have been shown toresult in significant increases in tadalafil plasma levels.Much like sildenafil, tadalafil is under clinical investigationfor managing PAH.
No severe negative reactions. No perceived facial flushing or sight abnormalities following medication. Rare cases of headache and indigestion.
In a study of 348 cases of mild to severe erectile dysfunction, patients were randomly given 20mg of Cialis or a placebo. Results showed that in comparison to the placebo group, patients who took Cialis experienced improved intercourse success in the 24-36 hours following medication, with many patients achieving successful sexual intercourse twice in 36 hours. Side effect rate and severity were also no different from those of the placebo group. Over 5% of patients in the Cialis group experienced headaches and indigestion.