Cetrotide and ganirelix are essential in your IVF cycle for controlling follicle development and keeping your body on track during the cycle. We got all the details on how they work, and their potential side effects, from fertility nurse and Dandi co-founder Leyla Bilali, RN.

If you're getting ready for IVF and want to know what to expect with the antagonist protocol, this guide has all the details for you!

What are Cetrotide and Ganirelix? 

If your IVF treatment involves the antagonist protocol, Cetrotide and Ganirelix will likely be part of your medication regimen. Both are brand names of the same type of medication, known as antagonists, used to manage follicle development. 

The purpose of an antagonist is to ensure all your follicles grow together, rather than allowing one or two to dominate, which can happen in a natural cycle. By keeping follicles developing at the same pace, Cetrotide and Ganirelix help your doctor control ovulation timing and optimize egg retrieval.

Why are Antagonists Important in IVF? 

Leyla explains that antagonists help follicles grow as a “cohort,” so they stay grouped together. This approach prevents your body from allowing one follicle to mature faster, which would typically lead to ovulation. Instead, Cetrotide or Ganirelix temporarily delays ovulation, allowing the follicles to develop evenly and keeping them on schedule for retrieval.

When Do You Start Cetrotide or Ganirelix? 

Timing for antagonist medications is unique to each patient. Typically, they’re introduced a few days after the start of your cycle, once your follicles begin to grow. Leyla mentions that for “quick responders,” this may be as early as day three or four. The timing depends on how your body is responding to the initial medications that stimulate follicle growth, so it’s important to follow your doctor’s monitoring plan to know precisely when to start.

How are Cetrotide and Ganirelix Administered? 

Both medications are administered via subcutaneous injections, which means they go just below the skin. Common injection sites include the abdomen, specifically the fatty tissue around it, or the outer thigh. If you’re already familiar with abdominal injections, this administration route should feel relatively similar to other IVF injections.

Side Effects of Cetrotide and Ganirelix 

All IVF medications can come with side effects, and Cetrotide and Ganirelix are no different. Patients often experience symptoms like bloating, cramping, or feeling foggy-headed. Leyla also notes that Cetrotide can sometimes cause a mild skin reaction around the injection site, resembling hives. While this can be concerning, it’s actually a common response and not an allergic reaction. Typically, this reaction resolves within a couple of hours.

With Ganirelix, Leyla mentions that the needle might feel slightly less smooth than others, requiring a bit more pressure to inject. Although this can be a little uncomfortable, it’s generally well-tolerated and not indicative of any serious issue.

Starting IVF medications like Cetrotide and Ganirelix may seem daunting, but understanding their purpose and what to expect with administration can make the process easier. Remember, these medications work to support your cycle by synchronizing follicle growth and keeping your treatment on track. If you have questions or notice any side effects, always reach out to your fertility clinic for guidance.

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