Metoprolol is available as two different salts: metoprolol tartrate and metoprolol succinate.

The main difference between metoprolol tartrate and metoprolol succinate is that metoprolol tartrate is only available as an immediate-release tablet which means it must be taken several times per day, whereas metoprolol succinate is an extended-release tablet that can be taken once a day. As a result, there are differences in the dosages and indications for both metoprolol tartrate and metoprolol succinate and they are not considered interchangeable.

• Both metoprolol tartrate and metoprolol succinate are used to lower blood pressure and relieve symptoms of angina in people with heart disease.
• Metoprolol tartrate may also be used to reduce the risk of death or another heart attack when given immediately following a heart attack, and to lower the risk of a heart attack in people with heart disease.
• Metoprolol succinate should not be used to prevent heart attacks.
• Extended-release metoprolol succinate may be beneficial in people with certain types of heart failure.
• An injectable form of metoprolol tartrate is available which may be given by health care providers for people with unstable angina or arrhythmia.
• Metoprolol tartrate may be used off-label for other conditions such as migraine prevention and to treat certain arrhythmias.

Both metoprolol tartrate and metoprolol succinate are classified as "selective" beta-blockers which means they are less likely to affect breathing and insulin response than nonselective beta-blockers. Generic forms are available.