What the label lists and what reports show
Nafarelin side effects
Nafarelin's FDA label: “In these 155 patients treated for an average of 41 months and as long as 80 months (6.7 years), adverse events most frequently reported (>3% of patients) consisted largely of episodes occurring during the first 6 weeks of treatment as a result of the …” FAERS holds 272 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is ovarian hyperstimulation syndrome (48 reports).
- No generic listed
Check it at the source: the nafarelin FDA label on DailyMed (effective March 5, 2026, Pfizer Laboratories Div Pfizer Inc); the FDA FAERS public dashboard.
What does the patient leaflet say about side effects?
From the patient leaflet: What are the possible side effects of SYNAREL?SYNAREL may cause serious side effects, including: • See " What is the most important information I should know about SYNAREL " • in the first month of treatment, SYNAREL can cause an increase in some hormones. During this time you may notice more signs of puberty in your child, including vaginal bleeding and breast enlargement in girls. Within 1 month of treatment, you should see signs in your child that puberty is stopping. • increased pressure in the fluid around the brain can happen in children taking gonadotropin releasing hormone (GnRH) agonist medicines including SYNAREL. […]
Source: FDA drug label, Pfizer Laboratories Div Pfizer Inc, effective March 5, 2026 (SPL set d0aa57cb-d2f4-46d7-af43-7c8b06aa81a6), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsIn these 155 patients treated for an average of 41 months and as long as 80 months (6.7 years), adverse events most frequently reported (>3% of patients) consisted largely of episodes occurring during the first 6 weeks of treatment as a result of the transient stimulatory action of nafarelin upon the pituitary-gonadal axis: acne (10%) transient breast enlargement (8%) vaginal bleeding (8%) emotional lability (6%) [see Warnings ] transient increase in pubic hair (5%) body odor (4%) seborrhea (3%) Hot flashes, common in adult women treated for endometriosis, occurred in only 3% of treated children and were transient.
From the label: adverse reactions, continuedIn clinical trials of 155 pediatric patients, 2.6% reported symptoms suggestive of drug sensitivity, such as shortness of breath, chest pain, urticaria, rash, and pruritus. In these 155 patients treated for an average of 41 months and as long as 80 months (6.7 years), adverse events most frequently reported (>3% of patients) consisted largely of episodes occurring during the first 6 weeks of treatment as a result of the transient stimulatory action of nafarelin upon the pituitary-gonadal axis: acne (10%) transient breast enlargement (8%) vaginal bleeding (8%) emotional lability (6%) [see Warnings ] transient increase in pubic hair (5%) body odor (4%) seborrhea (3%) Hot flashes, common in adult women treated for endometriosis, occurred in only 3% of treated children and were transient. Other adverse events thought to be drug-related, and occurring in >3% of patients were rhinitis (5%) and white or brownish vaginal discharge (3%). Approximately 3% of patients withdrew from clinical trials due to adverse events. In one male patient with concomitant congenital adrenal hyperplasia, and who had discontinued treatment 8 months previously to resume puberty, adrenal rest tumors were found in the left testis. Relationship to SYNAREL is unlikely. …
Source: FDA drug label, Pfizer Laboratories Div Pfizer Inc, effective March 5, 2026 (SPL set d0aa57cb-d2f4-46d7-af43-7c8b06aa81a6), via openFDA; the full label on DailyMed
What do FAERS reports show?
272 reports list nafarelin among the medicines taken, each a report of something that happened, not proof the medicine caused it; 9 are coded as a death and 97 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 21 reactions below, 4 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Nafarelin: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions