Abelacimab
is an investigational human monoclonal antibody targeting both inactive and active Factor XI, a key coagulation factor. Its mechanism of action involves potent and sustained Factor XI inhibition, leading to a significant reduction in Factor XI levels and prolongation of the activated partial thromboplastin time (aPTT). Pharmacokinetic advantages include a reduced risk of drug-drug interactions due to its non-metabolism via the cytochrome P-450 system and lack of P-glycoprotein substrate activity. Furthermore, dosage adjustments are not required for age, renal, or hepatic impairment. Clinical trials are currently evaluating abelacimab's efficacy and safety in various indications. The ongoing LILAC-TIMI 76 trial is assessing its potential in atrial fibrillation patients unsuitable for standard anticoagulation therapies. Additionally, the ASTER and MAGNOLIA trials are comparing abelacimab with established anticoagulants (apixaban and dalteparin, respectively) for venous thromboembolism prophylaxis in cancer patients. Abelacimab remains an investigational agent and is not yet approved for any therapeutic use.

A Jarisch–Herxheimer reaction is a body’s response to endotoxin-like substances released when bacteria are killed during antibiotic treatment. It’s been linked to syphilis, Lyme disease, leptospirosis, and relapsing fever. It usually happens 1 to 12 hours after the first antibiotic dose and doesn’t happen again with subsequent treatments. Symptoms include feeling tired, fever, redness, and a fast heartbeat. This can sometimes lead to low blood pressure because the blood vessels in the extremities dilate.

Procaine penicillin can cause a serious reaction if accidentally given IV instead of IM. It’s like a sudden rush of fear, with delusions and hallucinations. Patients might need help restraining themselves. The reaction usually goes away within 20 minutes. Sometimes, patients might have a seizure, which should be stopped with IV or PR diazepam.

• Purpuric rash • Raynaud’s • Polyarthralgia • Positive rheumatoid factor (RF) • Low C4 • Suggestive of
cyroglobulinaemia