What the label lists and what reports show
Conestat alfa side effects
Conestat alfa's FDA label: “The most common adverse reactions (≥ 2%) reported in all clinical trials were headache, nausea, and diarrhea.” FAERS holds 6,234 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 pharyngeal swelling (360 reports).
- No generic listed
Check it at the source: the conestat alfa FDA label on DailyMed (effective April 30, 2020); 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 RUCONEST?Like all medicines, RUCONEST can cause side effects, although not everybody gets them. Allergic reactions may occur with RUCONEST. Call your healthcare provider or the emergency department immediately if you have any of the following symptoms after receiving RUCONEST: wheezing difficulty breathing chest tightness turning blue (look at lips and gums) fast heartbeat swelling faintness rash hives In clinical studies, the most severe side effect reported in a person who received RUCONEST was a severe allergic reaction in a subject who was allergic to rabbits. Other side effects patients experienced during clinical research studies include: headache nausea diarrhea These are not all the possible side effects of RUCONEST. If any of the side effects get serious, or if you notice any side effects not listed in the leaflet, please inform your healthcare provider or pharmacist. […]
Source: FDA drug label, Pharming Healthcare Inc., effective April 30, 2020 (SPL set 66d3fecb-32a4-7781-e053-2a91aa0a83ca), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsThe most common adverse reactions (≥ 2%) reported in all clinical trials were headache, nausea, and diarrhea.
A table the label prints in its adverse reactions section without a title; its column headings name the groups compared
| MedDRA Preferred Term | RUCONEST 100 U/kg (N=29) n (%) | RUCONEST 50 U/kg* (N=66) n (%) | Placebo** (N=47) n (%) |
|---|---|---|---|
| Total number of patients with adverse reactions | 4 (14%) | 6 (9%) | 13 (28%) |
| Headache | 3 (10%) | 0 | 2 (4%) |
| Sneezing | 0 | 1 (2%) | 0 |
| Angioedema | 1 (3%) | 0 | 0 |
| Erythema marginatum | 0 | 1 (2%) | 0 |
| Skin burning sensation | 0 | 1 (2%) | 0 |
| Back pain | 0 | 2 (3%) | 0 |
| C-reactive protein increased | 0 | 1 (2%) | 0 |
| Fibrin D-dimer increased | 0 | 1 (2%) | 0 |
| Vertigo | 1 (3%) | 0 | 0 |
| Procedural headache | 0 | 1 (2%) | 0 |
| Lipoma | 0 | 1 (2%) | 0 |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
From the label: adverse reactions, continuedThe serious adverse reaction in clinical studies of RUCONEST was anaphylaxis. The most common adverse reactions (≥ 2%) reported in all clinical trials were headache, nausea, and diarrhea. The serious adverse reaction reported in clinical trials was anaphylactic reaction. ( 6 ) The common adverse reactions (≥ 2%) reported in clinical trials were headache, nausea, and diarrhea. ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Pharming Healthcare Inc. at 1-800-930-5221 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, the adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in clinical practice. The RUCONEST clinical development program evaluated a combined total of 940 administrations in 236 subjects (symptomatic and non-symptomatic). In clinical studies, a total of 205 symptomatic HAE patients received treatment with RUCONEST for a combined total of 650 acute angioedema attacks. Among these HAE patients, 83 were treated for a single HAE attack and 122 were treated for multiple attacks. …
Source: FDA drug label, Pharming Healthcare Inc., effective April 30, 2020 (SPL set 66d3fecb-32a4-7781-e053-2a91aa0a83ca), via openFDA; the full label on DailyMed
What do FAERS reports show?
6,234 reports list conestat alfa among the medicines taken, each a report of something that happened, not proof the medicine caused it; 24 are coded as a death and 1,278 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 14 reactions below, 2 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.
Reports received each year
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?
- Conestat alfa: 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