ISOSORBIDE MONONITRATE

Isosorbide mononitrate (ISMN), an organic nitrate and the major biologically active metabolite of isosorbide dinitrate (ISDN), is a vasodilator with effects on both arteries and veins. Each tablet, for oral administration, contains either 30 mg, 60 mg or 120 mg of isosorbide mononitrate in an extended-release formulation. In addition, each tablet contains the following inactive ingredients: colloidal silicon dioxide, hydrogenated castor oil, hypromellose, lactose monohydrate, magnesium stearate and microcrystalline cellulose. The molecular formula of ISMN is C 6 H 9 NO 6 and the molecular weight is 191.14. The chemical name for ISMN is 1,4:3,6-dianhydro-,D-glucitol 5-nitrate; the compound has the following structural formula: ISMN is a white, crystalline, odorless compound which is stable in air and in solution, has a melting point of about 90°C, and an optical rotation of +144° (2% in water, 20°C). Isosorbide mononitrate is freely soluble in water, ethanol, methanol, chloroform, ethyl acetate, and dichloromethane. FDA approved dissolution specifications differ from that of the USP. structuralformula--

Isosorbide mononitrate extended-release tablets are indicated for the prevention of angina pectoris due to coronary artery disease. The onset of action of oral isosorbide mononitrate is not sufficiently rapid for this product to be useful in aborting an acute anginal episode.

The recommended starting dose of isosorbide mononitrate extended-release tablets, USP is 30 mg (given as a single 30 mg tablet or as 1/2 of a 60 mg tablet) or 60 mg (given as a single tablet) once daily. After several days, the dosage may be increased to 120 mg (given as a single 120 mg tablet or as two 60 mg tablets) once daily. Rarely, 240 mg may be required. The daily dose of isosorbide mononitrate extended-release tablets, USP should be taken in the morning on arising. Isosorbide mononitrate extended-release tablets, USP should not be chewed or crushed and should be swallowed together with a half-glassful of fluid.

Isosorbide mononitrate extended-release tablets are contraindicated in patients who have shown hypersensitivity or idiosyncratic reactions to other nitrates or nitrites.

The table below shows the frequencies of the adverse events that occurred in >5% of the subjects in three placebo-controlled North American studies, in which patients in the active treatment arm received 30 mg, 60 mg, 120 mg, or 240 mg of isosorbide mononitrate extended-release tablets once daily. In parentheses, the same table shows the frequencies with which these adverse events were associated with the discontinuation of treatment. Overall, 8% of the patients who received 30 mg, 60 mg, 120 mg, or 240 mg of isosorbide mononitrate in the three placebo-controlled North American studies discontinued treatment because of adverse events. Most of these discontinued because of headache. Dizziness was rarely associated with withdrawal from these studies. Since headache appears to be a dose-related adverse effect and tends to disappear with continued treatment, it is recommended that ISMN treatment be initiated at low doses for several days before being increased to desired levels. FREQUENCY AND ADVERSE EVENTS (DISCONTINUED)* Three Controlled North American Studies Dose Placebo 30 mg 60 mg 120 mg** 240 mg** Patients 96 60 102 65 65 Headache 15% (0%) 38% (5%) 51% (8%) 42% (5%) 57% (8%) Dizziness 4% (0%) 8% (0%) 11% (1%) 9% (2%) 9% (2%) *Some individuals discontinued for multiple reasons. **Patients were started on 60 mg and titrated to their final dose. In addition, the three North American trials were pooled with 11 controlled trials conducted in Europe. Among the 14 controlled trials, a total of 711 patients were randomized to isosorbide mononitrate extended-release tablets. When the pooled data were reviewed, headache and dizziness were the only adverse events that were reported by >5% of patients. Other adverse events, each reported by 5% of exposed patients, and in many cases of uncertain relation to drug treatment, were: Autonomic Nervous System Disorders: Dry mouth, hot flushes. Body as a Whole: Asthenia, back pain, chest pain, edema, fatigue, fever, flu-like symptoms, malaise, rigors. Cardiovascular Disorders, General: Cardiac failure, hypertension, hypotension. Central and Peripheral Nervous System Disorders: Dizziness, headache, hypoesthesia, migraine, neuritis, paresis, paresthesia, ptosis, tremor, vertigo. Gastrointestinal System Disorders: Abdominal pain, constipation, diarrhea, dyspepsia, flatulence, gastric ulcer, gastritis, glossitis, hemorrhagic gastric ulcer, hemorrhoids, loose stools, melena, nausea, vomiting. Hearing and Vestibular Disorders: Earache, tinnitus, tympanic membrane perforation. Heart Rate and Rhythm Disorders: Arrhythmia, arrhythmia atrial, atrial fibrillation, bradycardia, bundle branch block, extrasystole, palpitation, tachycardia, ventricular tachycardia. Liver and Biliary System Disorders: SGOT increase, SGPT increase. Metabolic and Nutritional Disorders: Hyperuricemia, hypokalemia. Musculoskeletal System Disorders: Arthralgia, frozen shoulder, muscle weakness, musculoskeletal pain, myalgia, myositis, tendon disorder, torticollis. Myo-, Endo-, Pericardial and Valve Disorders: Angina pectoris aggravated, heart murmur, heart sound abnormal, myocardial infarction, Q wave abnormality. Platelet, Bleeding and Clotting Disorders: Purpura, thrombocytopenia. Psychiatric Disorders : Anxiety, concentration impaired, confusion, decreased libido, depression, impotence, insomnia, nervousness, paroniria, somnolence. Red Blood Cell Disorder: Hypochromic anemia. Reproductive Disorders, Female: Atrophic vaginitis, breast pain. Resistance Mechanism Disorders: Bacterial infection, moniliasis, viral infection. Respiratory System Disorders: Bronchitis, bronchospasm, coughing, dyspnea, increased sputum, nasal congestion, pharyngitis, pneumonia, pulmonary infiltration, rales, rhinitis, sinusitis. Skin and Appendages Disorders: Acne, hair texture abnormal, increased sweating, pruritus, rash, skin nodule. Urinary System Disorders: Polyuria, renal calculus, urinary tract infection. Vascular (Extracardiac) Disorders: Flushing, intermittent claudication, leg ulcer, varicose vein. Vision Disorders: Conjunctivitis, photophobia, vision abnormal. In addition, the following spontaneous adverse event has been reported during the marketing of isosorbide mononitrate: syncope.