Pain at the injection site, nausea, or vomiting may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly.
Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.
Tell your doctor right away if you have any serious side effects, including: joint/muscle pain, vision changes, signs of a new infection (such as sore throat that doesn't go away, fever, chills), easy bruising/bleeding, unusual tiredness, mental/mood changes (such as confusion, hallucinations, depression, agitation).
This medication may rarely cause a severe intestinal condition (Clostridium difficile-associated diarrhea) due to a type of resistant bacteria. This condition may occur during treatment or weeks to months after treatment has stopped. Tell your doctor right away if you develop: diarrhea that doesn't stop, abdominal or stomach pain/cramping, blood/mucus in your stool.
Do not use anti-diarrhea or opioid medications if you have any of these symptoms because these products may make them worse.
Use of this medication for prolonged or repeated periods may result in oral thrush or a new yeast infection. Contact your doctor if you notice white patches in your mouth, a change in vaginal discharge, or other new symptoms.
When used to treat syphilis and certain other infections, this medication may cause a reaction that occurs several hours after starting treatment and can last up to 24 hours. Tell your doctor right away if you have any of these symptoms: headache, fever/chills, sweating, joint/muscle pain, fast heartbeat, dizziness, worsening of skin sores or other disease symptoms.
Get medical help right away if you have any very serious side effects, including: pain/redness/swelling/numbness/weakness of arms/legs, change in skin color near the injection site or on arms/legs, severe pain/peeling skin at the injection site, muscle cramps/weakness around the injection site, inability to move (paralysis), chest pain, swollen lymph nodes, severe stomach/abdominal pain, nausea/vomiting that doesn't stop, yellowing eyes/skin, irregular heartbeat, seizures, pink/bloody/dark urine, signs of kidney problems (such as a change in the amount of urine).
A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.
This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.
In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.
In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.