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Reporting a Medication Error

Humatrope Medicine Cartridges and the HumatroPen Size Must Be a Match!

Published July 1, 2024

Hormones are substances that play an important role in how our body functions. For example, human growth hormone (HGH) helps in building muscles and bone structure as children develop. It also plays a role in maintaining normal body structure and metabolism in adults. HGH is normally produced by the body. But some children and adults have low levels of HGH and are prescribed Humatrope (somatropin), a manmade growth hormone.

Humatrope is a medicine that is given as an injection under the skin using a pen-injector called a HumatroPen. The HumatroPen holds a cartridge that contains the medicine (Figure 1). Once the cartridge of the medicine is empty, it should be replaced with a new cartridge and the pen-injector can be reused.

Figure 1. An example of a 6 mg Humatrope cartridge and HumatroPen ready for injection.

Humatrope cartridges come in three different strengths (e.g., 6 mg, 12 mg, 24 mg). The HumatroPen also comes in three different sizes to match the cartridge strengths (e.g., 6 mg, 12 mg, 24 mg). The strength of the Humatrope cartridge must match the HumatroPen to provide the correct dose of medicine (Figure 2). For example, a 6 mg cartridge of Humatrope must be used with a 6 mg HumatroPen. Unfortunately, errors can happen when the strength of the cartridge is changed but the previous HumatroPen device is used. This is what happened in an error report we received.

Figure 2. The HumatroPen and Humatrope cartridges come in three strengths/sizes (6 mg, 12 mg, and 24 mg). The pen and cartridge strength/size must match to deliver the correct amount of medicine.

A child, who had been receiving Humatrope 6 mg cartridges, was given a new prescription for 12 mg cartridges. The new prescription was filled at the pharmacy and the child’s parents began giving the new dose. After a few days, the parents noticed the cartridge was running out faster than expected and contacted the pharmacy. The pharmacist determined the correct strength cartridge (12 mg) was being used but it had been placed into the wrong size HumatroPen (6 mg instead of 12 mg). HumatroPens are not dispensed from pharmacies. They are usually provided by the doctor prescribing the medicine or they need to be obtained directly from the manufacturer (Lilly).

Here's what you can do: If you or a family member need to take Humatrope, make sure you understand how the medicine is given. Make sure that the strength of the Humatrope cartridge and the size of the HumatroPen match. The size of the HumatroPen is shown on the top of the injection button and at the pen-injector's base (Figure 3). The strength of Humatrope is near the drug name on the cartridge. If the pen size and cartridge strength do not match, do not use them. Contact your doctor to obtain the correct HumatroPen size. If your doctor changes the dosage of Humatrope from what was previously used, be sure to obtain the matching size HumatroPen.

Figure 3. The HumatroPen's size is located at the top (right) of the injection button and the pen-injector's base (left).

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