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:
More common
Black, tarry stools
chills
cough
feeling of fullness
fever
lower back or side pain
painful or difficult urination
pale skin
right upper abdominal pain and fullness
sore throat
stomach pain
swelling or inflammation of the mouth
swollen lymph nodes
ulcers, sores, or white spots in the mouth
unusual bleeding or bruising
unusual tiredness or weakness
Rare
Confusion
diarrhea
fast, shallow breathing
general feeling of discomfort
loss of appetite
mood or mental changes
muscle pain, tenderness, weakness, or cramping
nausea
seizures
sleepiness
stomach discomfort
Incidence not known
Back or leg pain
bleeding gums
blistering, peeling, or loosening of the skin
bloating
blood in the urine
blurred vision or other change in vision
bone pain
burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
clay-colored stools
constipation
dark urine
decreased appetite
decreased urine output
difficult or labored breathing
difficulty in moving
difficulty in swallowing
dilated neck veins
dizziness
extreme tiredness or weakness
fainting
fast, irregular, or pounding heartbeat
general body swelling
general tiredness and weakness
headache
high fever
hives, skin rash
hoarseness
increased need to urinate
indigestion
irregular breathing
irritation or soreness of the mouth
joint or muscle pain
lack of coordination
large, hive-like swelling on the face, eyelids, lips, tongue, throat, hands, legs, feet, or genitals
light-colored stools
muscle pain, cramp, spasm, or stiffness
nosebleeds
pains in the stomach, side, or abdomen, possibly radiating to the back
passing urine more often
puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
red skin lesions, often with a purple center
red, irritated eyes
redness, soreness, or itching skin
runny nose
shakiness in the legs, arms, hands, or feet
shivering
sores, welts, or blisters
stabbing pain
sweating
swollen joints
swollen or painful glands
tightness in the chest
trouble sleeping
unexplained bleeding or bruising
unpleasant breath odor
vomiting
vomiting of blood
weight gain
yellow eyes or skin
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:
More common
Difficulty having a bowel movement
headache (severe)
lack or loss of strength
muscle soreness
weight loss
Less common
Bluish-brown colored bands on nails
changes in skin color
Incidence not known
Belching
heartburn
stomach cramps
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.
 Zidovudine side effects (more detail)
