Chlormethine (INN, BAN), also known as mechlorethamine (USAN, USP), mustine, HN2, and (in post-Soviet states) embikhin (эмбихин), is a nitrogen mustard sold under the brand name Mustargen among others. It is the prototype of alkylating agents, a group of anticancer chemotherapeutic drugs. It works by binding to DNA, crosslinking two strands and preventing cell duplication. It binds to the N7 nitrogen on the DNA base guanine. As the chemical is a blister agent, its use is strongly restricted within the Chemical Weapons Convention where it is classified as a Schedule 1 substance. Mechlorethamine belongs to the group of nitrogen mustard alkylating agents. Uses It has been derivatized into the estrogen analogue estramustine phosphate, used to treat prostate cancer. It can also be used in chemical warfare where it has the code-name HN2. This chemical is a form of nitrogen mustard gas and a powerful vesicant. Historically, some uses of mechlorethamine have included lymphoid malignancies such as Hodgkin's disease, lymphosarcoma, chronic myelocytic leukemia, polycythemia vera, and bronchogenic carcinoma Mechlorethamine is often administered intravenously, but when compounded into a topical formulation it can also be used to treat skin diseases. There have been studies demonstrating that topical administration of mechlorethamine has efficacy in mycosis fungoides-type cutaneous T cell lymphoma. Another important use of chlormethine is in the synthesis of pethidine (meperidine). Side effects and toxicity Mechlorethamine is a highly toxic medication, especially for women who are pregnant, breastfeeding, or of childbearing age. At high enough levels, exposure can be fatal. The adverse effects of mechlorethamine depend on the formulation. When used in chemical warfare, it can cause immunosuppression and damage to mucous membranes of the eyes, skin, and respiratory tract. Mucous membranes and damp or damaged skin are more affected by exposure to HN-2. Though symptoms of exposure are generally delayed, the DNA damage it causes occurs very quickly. More serious exposures cause symptoms to develop sooner. Eye symptoms develop first, in the first 1–2 hours (severe exposure) or 3–12 hours (mild to moderate exposure) followed by airway (2-6/12–24 hours) and skin symptoms (6–48 hours). Hot, humid weather shortens the latent (symptom-free) period. Symptoms of toxic exposure to HN-2 vary based on the route of exposure. Eye exposure causes lacrimation (tear production), burning, irritation, itching, a feeling of grittiness or dryness, blepharospasm (spasms of the eyelid), and miosis (pinpoint pupils). More severe cases cause edema (swelling from fluid accumulation) in the eyelids,