Difference Between Metoprolol Succinate And Metoprolol Tartrate
Metoprolol succinate (Toprol XL) is the extended release version of metoprolol while metoprolol tartrate (Lopressor) is the immediate release version.
Is it safe to spilt a metoprolol tartrate 25 mg in half? I am doing this with the Toprol XL but I am still feeling tired and my doctor told me to try taking 12.5 twice daily of the tartrate instead of 12.5 of the Toprol XL. Would this be safe and would it make me less tired? I am taking Toprol XL for palpitations only and not for hypertension.
Metoprolol tartrate (brand name Lopressor) and metoprolol succinate (Toprol XL) are considered different salt forms of the same drug (metoprolol). Changing the 'salt form' of a drug can significantly impact a variety of properties of how a drug acts in our body, including (1, 2):
- Absorption characteristics
- Dissolution characteristics
When it comes to metoprolol products:
- Metoprolol succinate (Toprol XL) is considered the extended-release (i.e. long-acting) version of metoprolol.
- Metoprolol tartrate (Lopressor) is considered the immediate-release (i.e. short-acting) version of metoprolol.
Differences In Indication
Although the distinction between immediate-release and extended-release metoprolol appears relatively straightforward, it is important to note that they have different FDA approved indications:
- Both metoprolol tartrate (Lopressor, etc) and metoprolol succinate (Toprol XL) are FDA approved for the treatment of hypertension (i.e. high blood pressure) (3, 4).
- Only metoprolol succinate (Toprol XL) in FDA approved for the treatment of heart failure and studies have shown that it improves survival rate when compared to metoprolol tartrate (5).
- Metoprolol tartrate (Lopressor), being an immediate release medication, is generally recommended to be dosed twice daily at even intervals.
- Metoprolol succinate (Toprol XL), being the extended release version, is generally recommended to be dosed once daily (every 24 hours).
Splitting Metoprolol Tartrate And Succinate
Both metoprolol tartrate (Lopressor) and metoprolol succinate (Toprol XL) can safely be cut or split. While this is expected with metoprolol tartrate (and most immediate release) products, it is unusual for an extended release product like Toprol XL to be able to be safely cut.
We wrote a more in-depth article regarding why Toprol XL can be split, which can be found here: Cutting Toprol XL. It basically has to do with how the extended release mechanism of Toprol XL works, and how the drug is distributed in the tablets. It should be noted that while they can be cut or split, they cannot be crushed.
The side effects of metoprolol tartrate and metoprolol succinate are similar and occur at a similar rate. When it comes to sedation, drowsiness and a general feeling of tiredness, the prescribing information for both drugs (Toprol XL and Lopressor) report the same incidence rate, about 10% (3, 4). Nevertheless, there is certainly a chance you may tolerate one better than the other and it may be worth trying the different version of the medication (as your doctor has recommended).
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