Metoprolol was first made in 1969

Metoprolol was first made in 1969. It is a ?1 receptor blocker and it is marketed with trade name Lopressor. It is used to treat high blood pressure, chest pain due to poor blood flow to the heart and an abnormally fast heart rate. It is also used to prevent further heart problems after myocardial infarction and to prevent headaches in those with migraines.
Metoprolol is administered orally or intravenously. The medication is taken twice a day. The extended-release formulation is taken once per day. Metoprolol may be combined with hydrochlorothiazide in a single tablet.
Common side effects are trouble sleeping, feeling tired, feeling faint and abdominal discomfort. Large doses may cause serious toxicity. It is safe in breastfeeding. Greater care is required with use in those with liver problems or asthma. Stopping this drug should be done slowly to decrease the risk of further health problems.
Medical uses
Metoprolol is used for treatment of hypertension, angina, acute myocardial infarction, supraventricular tachycardia, ventricular tachycardia, congestive heart failure and prevention of migraine headaches.
• Treatment of heart failure
• Vasovagal syncope
• Adjunct in treatment of hyperthyroidism
• Long QT syndrome especially for patients with asthma, as metoprolol’s ?1 selectivity tends to interfere less with asthma drugs which are often ?2-adrenergic receptor-agonist drugs
• Prevention of relapse into atrial fibrillation

Adverse effects
Side effects especially with higher doses are dizziness, drowsiness, fatigue, diarrhea, unusual dreams, trouble sleeping, depression and vision problems. Metoprolol may also reduce blood flow to the hands or feet, causing them to feel numb and cold, smoking may worsen this effect. Due to the high penetration across the blood-brain barrier, lipophilic beta blockers such as propranolol and metoprolol are more likely than other less lipophilic beta blockers to cause sleep disturbances such as insomnia and vivid dreams and nightmares.
Serious side effects that are advised to be reported immediately include symptoms of bradycardia, persistent symptoms of dizziness, fainting and unusual fatigue, bluish discoloration of the fingers and toes, numbness/tingling/swelling of the hands or feet, sexual dysfunction, erectile dysfunction, hair loss, mental/mood changes, depression, breathing difficulty, cough, dyslipidemia and increased thirst. Consuming alcohol while taking metoprolol may cause mild body rashes and is not advised.
Precautions
Metoprolol may worsen the symptoms of heart failure in some patients who may experience chest pain or discomfort, dilated neck veins, extreme fatigue, irregular breathing, an irregular heartbeat, shortness of breath, swelling of the face, fingers, feet, or lower legs, weight gain or wheezing. This medicine may cause changes in blood sugar levels or cover up signs of low blood sugar such as a rapid pulse rate. It also cause some people to become less alert than they are normally making it dangerous for them to drive or use machines. Greater care is required with use in those with liver problems or asthma. Stopping this drug should be done slowly to decrease the risk of further health problems.
Overdose
Excessive doses of metoprolol can cause severe hypotension, bradycardia, metabolic acidosis, seizures and cardiorespiratory arrest. Blood or plasma concentrations may be measured to confirm a diagnosis of overdose or poisoning in hospitalized patients or to assist in a medicolegal death investigation. Plasma levels are usually less than 200 ?g/l during therapeutic administration but can range from 1–20 mg/l in overdose victims.

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Pharmacokinetics
Metoprolol has a short half-life of 3 to 7 hours. It is taken at least twice daily or as a slow-release preparation. It undergoes ?-hydroxylation and O-demethylation as a substrate of the cytochrome liver enzymes CYP2D6 and a small percentage by CYP3A4, resulting in inactive metabolites.
Stereochemistry
Metoprolol contains a stereocenter and consists of two enantiomers. This is a racemate 1:1 mixture of (R)- and the (S)-form.