Cialis (tadalafil) - 2 indications

Scroll down for additional information on each indication:

• for the treatment of Erectile Dysfunction; approved December 2003
• for the treatment of the signs and symptoms of benign prostatic hyperplasia; approved October of 2011

General Information

Cialis (tadalafil) is a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5).

Cialis is specifically indicated for the treatment of:

• erectile dysfunction 
• the signs and symptoms of benign prostatic hyperplasia (BPH)

Cialis is supplied as tablets for oral administration. Scroll down for dosing/administration for each indication.

Mechanism of Action

Erections are caused by increased blood flow from the relaxation of penile arteries and corpus cavernosal smooth muscle. Cyclic GMP (cGMP) causes smooth muscle relaxation and increased blood flow into the corpus cavernosum. During sexual stimulation, tadalafil will inhibit phosphodiesterase type 5 PDE5, which increases the amount of cGMP in smooth muscles cells thus enhancing erectile function.

Preclinical studies showed that tadalafil is over 10,000-fold more potent for PDE5 than for PDE1, PDE2, PDE4, and PDE7 enzymes, which are found in the heart, brain, blood vessels, liver, leukocytes, skeletal muscle, and other organs.

Side Effects

Adverse events associated with the use of Cialis may include (but are not limited to) the following:

• Headache
• Dyspepsia
• Back pain
• Myalgia
• Nasal congestion
• Flushing
• Pain in limb

Indication 1 - for the treatment of Erectile Dysfunction

approved December 2003

Dosing/Administration

Cialis for use as needed:

• Starting dose: 10 mg as needed prior to sexual activity. Increase to 20 mg or decrease to 5 mg based upon efficacy/tolerability. Improves erectile function compared to placebo up to 36 hours post dose. Not to be taken more than once per day.

Cialis for once daily use:

• 2.5 mg taken once daily, without regard to timing of sexual activity. May increase to 5 mg based upon efficacy and tolerability. Take at approximately the same time every day. Cialis may be taken without regard to food

Clinical Trial Results

FDA approval of Cialis was based on 2 U.S. and 5 international randomized, multicenter, double-blinded, placebo-controlled trials. In total, Cialis has been evaluated in over 4,000 subjects. The primary outcome measures were the Erectile Function (EF) domain of the International Index of Erectile Function (IIEF) and Questions 2 and 3 from Sexual Encounter Profile (SEP). The IIEF is a 4-week recall questionnaire administered at the end of a treatment-free baseline period and at follow-up visits after enrollment. The IIEF EF domain has a 30-point total score, where higher scores reflect better erectile function. SEP is a diary in which subjects recorded each sexual attempt made during the study.

Results of the 2 U.S. trials demonstrated meaningful and statistically significant improvements in all efficacy variables, with positive effects being maintained over time. The trial enrolled 402 subjects, with an average age of 59 years, experiencing erectile dysfunction (ED). Cialis doses ranged from 2.5 to 20 mg, once daily as needed.

Results of the 5 international studies demonstrated statistically significant improvements in all 3 primary efficacy variables. Treatment effects did not diminish over time. In addition, data showed patient-reported improvement in erections across subjects with ED of all degrees of severity while taking Cialis, compared to placebo. The efficacy and safety studies enrolled 1112 subjects, with a mean age of 59. The trials included subjects with ED and with multiple conditions, including diabetes mellitus, hypertension, and other cardiovascular diseases.

Indication 2 - for the treatment of the signs and symptoms of benign prostatic hyperplasia

approved October of 2011

Dosing/Administration

5 mg, taken at approximately the same time every day. Cialis may be taken without regard to food.

Clinical Trial Results

The efficacy and safety of Cialis for once daily use for the treatment of the signs and symptoms of BPH was evaluated in 3 randomized, multinational, double-blinded, placebo-controlled, parallel-design, efficacy and safety studies of 12 weeks duration. Two of these studies were in men with BPH and one study was specific to men with both ED and BPH. The first study (Study J) randomized 1058 patients to receive either Cialis 2.5 mg, 5 mg, 10 mg or 20 mg for once daily use or placebo. The second study (Study K) randomized 325 patients to receive either Cialis 5 mg for once daily use or placebo. 

The primary efficacy endpoint in the two studies that evaluated the effect of Cialis for the signs and symptoms of BPH was the International Prostate Symptom Score (IPSS), a four week recall questionnaire that was administered at the beginning and end of a placebo run-in period and subsequently at follow-up visits after randomization. The IPSS assesses the severity of irritative (frequency, urgency, nocturia) and obstructive symptoms (incomplete emptying, stopping and starting, weak stream, and pushing or straining), with scores ranging from 0 to 35; higher numeric scores representing greater severity. Maximum urinary flow rate (Qmax), an objective measure of urine flow, was assessed as a secondary efficacy endpoint in Study J and as a safety endpoint in Study K. 

In each of these 2 trials, CIALIS 5 mg for once daily use resulted in statistically significant improvement in the total IPSS compared to placebo. Mean total IPSS showed a decrease starting at the first scheduled observation (4 weeks) in Study K and remained decreased through 12 weeks.