Impotence (ED) (cont.)
Tadalafil (Cialis)
What is tadalafil (Cialis)?
Tadalafil (Cialis) is the third oral medicine approved by the United FDA in
the US for the treatment of erectile dysfunction. Like sildenafil (Viagra) and
vardenafil (Levitra), tadalafil inhibits PDE5 (as described earlier).
How effective is tadalafil (Cialis)?
The safety and efficacy of tadalafil in the treatment of erectile dysfunction was evaluated in
22 clinical trials involving more than 4,000 men. Seven of these trials were
randomized, prospective, placebo-controlled studies of 12 weeks' duration. Two
of these studies (involving 402 men) were conducted in the Untied States, and
the other five studies (involving 1112 men) were conducted outside the Untied
states. Two of these trials were conducted in special erectile dysfunction
populations; one in men with diabetes mellitus, another in men who developed
erectile dysfunction after nerve-sparing prostate cancer surgery.
Effectiveness of tadalafil in these studies was assessed using a sexual
function questionnaire. Study participants also were asked if they were able to
achieve vaginal penetration and to maintain erections long enough for successful
intercourse.
In all seven trials, tadalafil was significantly better than placebo in
improving men's ability to achieve and maintain erections. Improvements in
erectile function was observed in some patients at 30 minutes after taking a
dose; and improvements can last for up to 36 hours after taking Cialis when
compared to placebo.
How should tadalafil (Cialis) be administered?
The recommended starting dose of tadalafil for most patients is 10 mg taken
orally approximately 1 hour before sexual activity. The dose may be adjusted
higher to 20 mg or lower to 5 mg depending on efficacy and tolerability. The
maximum recommended dosing frequency is once per day, although for many patients tadalafil can be taken less frequently since the improvement in erectile function
may last 36 hours. Tadalafil may be taken with or without food.
What are the side effects of tadalafil (Cialis)?
Tadalafil is generally well tolerated with only mild side effects. The most
common side effects reported include headache, indigestion, back pain, muscle
aches, facial flushing, and nasal congestion.
Back pain and muscle aches occurred in less than 7% of patients, and usually
occurred at 12 to 24 hours after taking tadalafil. The back pain and muscle
aches associated with tadalafil were characterized by mild to moderate muscle
discomfort in the lower back, buttocks and thighs, often aggravated by lying
down. The back and muscle aches resolved in most patients without treatment
within 48 hours. When treatment was necessary, acetaminophen (Tylenol) and
non-steroidal antiinflammatory drugs (NSAIDs) such as Motrin, Advil, or Aleve
were effective. Approximately 0.5% of all the patients using tadalafil
discontinued the drug due to back pain or muscle aches.
Reports of abnormal vision were rare, it occurred in less than 0.1% of
patients using tadalafil.
There have been rare reports of priapism (prolonged and painful erections
lasting more than 6 hours) with the use of oral PDE5 inhibitors such as
vardenafil, sildenafil and tadalafil. Patients with blood cell diseases such as
sickle cell anemia, leukemia, and multiple myeloma have higher than normal risks
of developing priapism. Priapism untreated can cause injury to the penile tissue
and lead to permanent loss of potency. If there is prolonged erection (longer
than 4 hours), immediate medical assistance should be sought.
Who should not use tadalafil (Cialis)?
Tadalafil can cause hypotension (abnormally low blood pressure, which can
lead to fainting and even shock) when given to patients who are taking nitrates.
Patients taking nitrates daily, even patients taking nitrates only once a day,
should not take tadalafil. Most commonly used
nitrates are medications to relieve angina (chest pain due to insufficient blood
supply to heart muscle because of narrowing of the coronary arteries). These
include nitroglycerine tablets, patches, ointments, sprays, pastes, and
isosorbide dinitrate and isosorbide mononitrate. Other nitrates such as amyl
nitrate and butyl nitrate are found in some recreational drugs called "poppers".
Tadalafil should not be used with alpha-blockers (except Flomax), medicines
used to treat high blood pressure and benign prostate hypertrophy (BPH), because
the combination of tadalafil and an alpha-blocker may lower the blood pressure
greatly and lead to dizziness and fainting. Examples of alpha-blockers include
tamsulosin (Flomax), terazosin (Hytrin), doxazosin (Cardura), alfuzosin
(Uroxatrol), and prazosin (Minipress). The only alpha-blocker that can be used
safely with tadalafil is tamsulosin (Flomax). When tadalafil (20 mg) was given
to healthy men taking 0.4 mg of Flomax daily, there was no significant decrease
in blood pressure and so patients on this dose of tamsulosin (Flomax) can be prescribed
tadalafil. The only alpha blocker that has not been tested with tadalafil is
alfuzosin (Uroxatrol) and no recommendations can be made regarding the interaction between
the two.
Tadalafil is not recommended for men with the following conditions:
- Unstable angina (chest pain due to coronary artery
disease that occurs at rest or with minimal physical exertion)
- Low blood pressure (a resting systolic blood pressure
less than 90mm Hg)
- Uncontrolled high blood pressure (greater than
170/110 mm Hg)
- Recent stroke or heart attack (within 6 months)
- Uncontrolled, potentially life-threatening abnormal
heart rhythms
- Severe liver disease
- Severe heart failure or disease of the heart's
valves, for example, aortic stenosis
- Retinitis pigmentosa
Therefore, men with these conditions should not use tadalafil without having
these conditions evaluated and stabilized first. For example, men with
uncontrolled high blood pressure should have their blood pressure controlled; and
men with potentially life-threatening abnormal heart rhythms should have these
rhythms controlled.
When there is angina or heart failure, the doctor may need to determine
whether the heart has enough reserve to safely carry out the work necessary for
sexual activity by performing cardiac treadmill stress testing.
What precautions should be taken when using tadalafil?
In most healthy men, some of the drug will remain in the body for more than 2
days after a single dose of tadalafil. Metabolism (clearing of the drug from the
body) of tadalafil can be slowed by liver disease, kidney disease, and
concurrent use of certain medications (such as erythromycin, ketoconazole, and
protease inhibitors). Slowed breakdown allows tadalafil to stay in the body
longer and potentially increase the risk for side effects. Therefore, the dose
and frequency of tadalafil has to be lowered in the following examples:
- Medications such as erythromycin, ketoconazole (Nizoral), itraconazole
(Sporanox), ritonavir (Norvir), and indinavir (Crixivan) can slow the
breakdown of tadalafil. Therefore men taking these medications should not take
more than 10 mg of tadalafil and should not take tadalafil more frequently
than every 72 hours.
- No tadalafil dose adjustment is necessary for men
with only mild kidney disease. Men with moderately severe kidney impairment
should start tadalafil at 5 mg every 24 hours, and not to exceed the maximum
dose of 10 mg taken every 48 hours. In men with severe kidney disease and on
dialysis, the maximum dose should not exceed 5 mg.
- Men with severe liver disease should not take tadalafil. Men with mild to
moderate liver disease should not exceed tadalafil dose of 10 mg once daily.
Next: Intracavernosal injections »
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