Legislation
On 23 September 2011, the Medicines and Healthcare products Regulatory Agency (MHRA) granted the Intas Pharmaceuticals Limited marketing authorization (licences) for metoprolol tartrate (50 mg and 100 mg tablets) for medicinal prescription only; this was after it was established that there were no new or unexpected safety concerns and that the benefits of metoprolol tartrate were greater than the risks. Metoprolol tartrate is a generic version of Lopressor, which was licensed and authorized on 6 June 1997 to Novartis Pharmaceuticals. In sport
Because beta blockers can be used to reduce heart rate and minimize tremors, which can enhance performance in sports such as archery, Metoprolol is banned by the world anti-doping agency in some sports. Some bans, as in all forms of billiards, darts, and golf, apply during competition only. In others, such as riflery competition, any form of beta blocker is banned by the National Collegiate Athletic Association.Urine tests are used to detect if beta blockers are present. Uncharged drugs and/or metabolites of beta blockers can be analysed by gas chromatography-mass spectrometry in selected ion monitoring (GC-MS-SIM). However, in modern times it is increasingly difficult to detect the presence of beta blockers used for sports doping purposes. A disadvantage to using GC-MS-SIM is that prior knowledge of the molecular structure of the target drugs/metabolites is required. Modern times have shown a variance in structures and hence novel beta blockers can go undetected.
Metoprolol, sold under the brand name Lopressor, among others, is a selective β1 receptor blocker medication. It is used to treat high blood pressure, chest pain due to poor blood flow to the heart, and a number of conditions involving an abnormally fast heart rate. By working on the beta-1 receptor of the cardiac muscle cells, it yields both a chronotropic and inotropic effect. It is also used to prevent further heart problems after myocardial infarction and to prevent headaches in those with migraines.Metoprolol is sold in formulations that can be taken by mouth or given intravenously. The medication is often taken twice a day. The extended-release formulation is taken once per day. Metoprolol may be combined with hydrochlorothiazide (a diuretic) in a single tablet.Common side effects include trouble sleeping, feeling tired, feeling faint, and abdominal discomfort. Large doses may cause serious toxicity. Risk in pregnancy has not been ruled out. It appears to be safe in breastfeeding. The metabolism of metoprolol can vary widely between patients, often as a result of hepatic impairment or CYP2D6 polymorphism. Care should be taken in patients with asthma; metoprolol should only be used in these patients when the benefits outweigh the risks, for example in heart failure. Stopping this drug should be done slowly to decrease the risk of further health problems.Metoprolol was first made in 1969, patented in 1970, and approved for medical use in 1982. It is on the World Health Organizations List of Essential Medicines. It is available as a generic drug.