Irritation at the implant site (such as bruising, pain, redness), mood swings, or headache may occur. In men using this medication for prostate cancer, hot flashes (flushing), increased sweating, night sweats, tiredness, swelling of the ankles/feet, or constipation may occur. In girls using this medication for early puberty, breast tenderness or abnormal vaginal bleeding may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly.
Rarely, breast tenderness/swelling may occur in men and boys as a result of lowered testosterone levels. Shrinking of the testicles and reduced sexual interest/ability may also occur in men. Talk to your doctor if these effects occur.
Remember that this medication has been prescribed because your doctor 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.
If you are a man using this medication for prostate cancer, tell your doctor right away if you have any serious side effects, including: new/worsening bone pain, easily broken bones, increased thirst/urination, mental/mood changes (such as depression).
Get medical help right away if you have any very serious side effects, including: chest/jaw/left arm pain, fast/irregular heartbeat, severe dizziness, fainting, weakness on one side of the body, trouble speaking, seizures.
Children using histrelin may be at risk for increased pressure around the brain (intracranial hypertension). Get medical help right away if your child has any of these very serious side effects: nausea/vomiting that doesn't stop, headache that is severe or doesn't go away, eye pain, vision changes (such as blurred/double vision, decreased vision), ringing in the ears.
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.