The most common adverse reactions observed in ? 2% of patients in the clinical studies for Anascorp were: vomiting, pyrexia, rash, nausea, and pruritus ^{FDA label}.

Severe hypersensitivity reactions, including anaphylaxis, may occur with Anascorp ^L2203, ^{FDA label}. Diligent patient monitoring for hypersensitivity reactions and preparation for intravenous therapy using epinephrine, corticosteroids, and diphenhydramine hydrochloride is recommended during the infusion. If an anaphylactic reaction occurs during the Anascorp infusion, case administration immediately, and administer warranted emergency medical care ^{FDA label}.

Patients with existing allergies to horse protein are at a higher risk for developing anaphylactic reactions. Patients who have had previous therapy with Anascorp or another equine antivenom/antitoxin may have become sensitized to equine proteins and be at an elevated risk for a severe hypersensitivity reaction ^{FDA label}.

Trace amounts of cresol from the manufacturing process are contained in Anascorp. Localized reactions and generalized myalgias have been observed with the use of cresol as an injectable excipient ^{FDA label}.

Monitor patients with follow-up visit(s) for signs and symptoms of delayed allergic reactions or serum sickness (symptoms include rash, fever, myalgia, arthralgia), and treat appropriately if necessary. Eight out of 1,534 (0.5%) patients in the clinical trials exhibited symptoms suggestive of serum sickness ^{FDA label}.

Anascorp is created from equine (horse) plasma, it may carry a risk of transmitting infectious agents, e.g., viruses ^{FDA label}.

The following adverse reactions have been identified during post-approval use of Anascorp: chest tightness, palpitations, rash, and pruritus. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure ^{FDA label}.