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What should I watch for?
If you notice any changes in your vision while taking this drug, call your doctor or health care professional as soon as possible. Stop using this medicine and call your health care provider right away if you have a loss of sight in one or both eyes.
Contact your doctor or health care professional right away if you have an erection that lasts longer than 4 hours or if it becomes painful. This may be a sign of a serious problem and must be treated right away to prevent permanent damage.
If you experience symptoms of nausea, dizziness, chest pain or arm pain upon initiation of sexual activity after taking this medicine, you should refrain from further activity and call your doctor or health care professional as soon as possible.
Do not drink alcohol to excess (examples, 5 glasses of wine or 5 shots of whiskey) when taking this medicine. When taken in excess, alcohol can increase your chances of getting a headache or getting dizzy, increasing your heart rate or lowering your blood pressure.
Using this medicine does not protect you or your partner against HIV infection (the virus that causes AIDS) or other sexually transmitted diseases.
Common and Rare Side Effects
Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor immediately if any of the following side effects occur:
burning feeling in the chest or stomach
burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
cloudy or bloody urine
increased frequency of urination
pain on urination
tenderness in the stomach area
behavior change similar to drunkenness
bleeding of the eye
cool and pale skin
deafness or hearing loss
decrease in amount of urine or the frequency of urination
difficulty in concentrating
dizziness or lightheadedness, especially when getting up suddenly from a lying or sitting position
dryness, redness, scaling, or peeling of the skin
fainting or faintness
fast, irregular, or pounding heartbeat
feeling of something in the eye
fever or chills
headache (severe or continuing)
increase in the size of the pupil
lower back or side pain
nausea (severe or continuing)
numbness of the hands
painful, swollen joints
prolonged, painful erection of penis
redness, burning, or swelling of the eyes
redness, itching, or tearing of the eyes
seeing shades of colors differently than before
sensitivity to light
skin lesions with swelling
swelling of the face, hands, feet, or lower legs
twitching of the muscles
unusual feeling of burning or stinging of the skin
unusual tiredness or weakness
vision loss, temporary
Incidence not known
Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
Aches or pains in the muscles
difficult or labored breathing
pain or tenderness around the eyes and cheekbones
redness of the skin
stomach discomfort following meals
stuffy or runny nose
unusually warm skin
Abdominal or stomach pain
clumsiness or unsteadiness
diarrhea or stomach cramps (severe or continuing)
difficulty in swallowing
increased amount of saliva
increased skin sensitivity
lack of coordination
loss of bladder control
numbness or tingling of the hands, legs, or feet
redness or irritation of the tongue
redness, soreness, swelling, or bleeding of the gums
ringing or buzzing in the ears
sensation of motion, usually whirling, either of one's self or of one's surroundings
sexual problems in men (continuing), including failure to experience a sexual orgasm
sores in the mouth and on the lips
trembling and shaking
waking to urinate at night
worsening of asthma
Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.
Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.