Split Metoprolol

Overview

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:

  • Absorption characteristics
  • Dissolution characteristics
  • Lipophilicity

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).
  • 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.

Differences In Dosing

  • 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.


Additional Information

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%.

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).


Summary

  • Metoprolol tartrate and metoprolol succinate are different salt forms of the same drug.
  • They have numerous differences with the most notable being that metoprolol tartrate is 'immediate-release' while metoprolol succinate is 'extended-release'.

  • References
    1. Effects of controlled-release metoprolol on total mortality, hospitalizations, and well-being in patients with heart failure: the Metoprolol CR/XL Randomized Intervention Trial in congestive heart failure (MERIT-HF). MERIT-HF Study Group. PubMed
    2. Toprol XL Prescribing Information. AccessFDA
    3. Lopressor Prescribing Information. AccessFDA
    4. Salt formation to improve drug solubility. PubMed
    5. Pharmaceutical salts: Theory, use in solid dosage forms and in situ preparation in an aerosol. Science Direct