Cialis
Cialis (tadalafil)
In this drug monograph:
Side Effects or Adverse Reactions
Table 1. Common and Serious Side Effects of Cialis
| Common Side Effects | Frequency |
|---|---|
| Headache | 3-15% |
| Dyspepsia | 4-10% |
| Back pain | 3-6% |
| Myalgia | 1-3% |
| Nasal pharyngitis | 2-6% |
| Nasal congestion | 3% |
| Serious Side Effects | Frequency |
| Change in Color Vision | <1% |
| NAION | rare |
| Priapsm | rare |
| Hearing loss | rare |
| Stevens-Johnson Syndrome | <2% |
| Exfoliative dermatitis | <2% |
| Angina* | <2% |
| Stroke | <2% |
| Myocardial infarction* | <2% |
| Severe hypotension* | <2% |
| Tachycardia | <2% |
* See warnings and precautions about use with antihypertensives and in patients with cardiovascular disease.
Drug Interactions
Cialis is a vasodilator and it is extensively metabolized by CYP3A4 liver enzymes. Therefore, combining Cialis with other vasodilators will increase the incidence of hypotension, and CYP3A4 inhibitors will increase the blood levels of Cialis.
Table 2. Cialis Drug Interactions
| Drug | Effect | Recommendation |
|---|---|---|
| Nitrates for example, isosorbide, nitroglycerin | Increased hypotension | Contraindicated |
| Alpha adrenergic blockers | Increased hypotension | Caution. Do not combine with alpha blockers for treatment of BPH. For ED, patients should be stable on alpha blocker prior to Cialis, and lowest Cialis dose should be used |
| Antihypertensives | Increased hypotension | Caution |
| Alcohol | Increased hypotension | Do not combine with substantial amounts of alcohol |
| Antacids (magnesuim hydroxide/aluminum hydroxide) | Reduced rate of absorption of Cialis, but total absorption is the same. | No recommendations |
| Ketoconazole, ritonavir, erythromycin, itraconazole, grapefruit juice, other HIV protease inhibitors | Inhibits CYP3A4 metabolism increasing blood levels of Cialis | Avoid combination of Cialis with CYP3A4 inhibitors if possible. Maximum dose is 10 mg every 72 hours as needed or 2.5 mg daily regardless of sexual activity |
| Rifampin, carbamazepine, phenytoin, phenobarbital | Increased metabolism via CYP3A4 liver enzymes with reduced blood levels of Cialis | Dosage adjustment is not required |
Efficacy of Cialis (tadalafil)
Erectile Dysfunction
- Lasts up to 36 hours and starts working within 15-30 minutes after ingestion.
- 62%-77% of patients taking 20 mg Cialis were able to initiate intercourse (insert penis) compared to 39%-43% of patients who received placebo. Change from baseline was 2% for placebo and 26%-32% for Cialis users.
- 50%-64% of Cialis users maintained their erection compared to 23%-25% of patients taking placebo. Change from baseline was 4%-5% for placebo and 34%-44% for Cialis users.
- Cialis versus Viagra: Cialis works within 15-30 minutes and lasts 36 hours while Viagra works within 30-60 minutes and lasts about 4 hours.
BPH (Benign Prostatic Hyperplasia)
After 12 weeks of treatment changes in total symptom score were -3.6 for placebo and -5.6 for patients taking Cialis 5 mg daily. Cialis was significantly better than placebo in reducing symptoms of BPH.
Pharmacology (Mechanism of Action)
Cialis is a selective phosphodiesterase type 5 (PDE5) inhibitor. Inhibition of PDE5 increases cGMP in smooth muscle cells. Cyclic GMP causes smooth muscle relaxation and increased blood flow into the corpus cavernosum, causing penile erection. How Cialis relieves symptoms of BPH is not understood. PDE5 also is present in smooth muscles of the prostate and bladder wall. Inhibiting PDE5 may increase CGMP concentrations leading to relaxation of smooth muscle in the prostate and bladder. Smooth muscle relaxation may improve blood flow to the urinary tract and widen the opening of the bladder neck, resulting in improved voiding.
Cialis Pill Identification and Imprint Code
Cialis 2.5 mg tablet is a yellow, almond film-coated tablet, with imprint "C 2 1/2".
Cialis 5 mg tablet is a yellow, almond film-coated tablet, with imprint "C 5".
Cialis 10 mg tablet is a yellow, almond film-coated tablet, with imprint "C 10".
Cialis 20 mg tablet is a yellow, almond film-coated tablet, with imprint "C 20".
Last reviewed on RxList: 6/8/2012
REFERENCE: FDA Prescribing Information.
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