Emend Side Effects: What to Expect and When to Call Your Doctor

Emend (aprepitant) is generally well-tolerated, especially considering it's used alongside chemotherapy—a treatment that itself causes side effects. But knowing what to expect from Emend specifically can help you distinguish medication side effects from chemotherapy effects and recognize warning signs that warrant a call to your care team.

Common Side Effects of Emend (Aprepitant)

The most frequently reported side effects with Emend include:

Fatigue or tiredness: One of the most common complaints; difficult to distinguish from chemotherapy-related fatigue, but often resolves within a few days after your aprepitant course ends

Diarrhea: Generally mild; stay hydrated and contact your care team if it's severe or persists

Hiccups: A notable side effect specific to aprepitant and other antiemetics in this class; usually transient

Loss of appetite: Common, particularly in the context of chemotherapy; eat small, frequent meals when possible

Abdominal pain or discomfort: Mild stomach pain has been reported in clinical trials; notify your doctor if pain is severe

Headache and dizziness: Generally mild; rest, adequate hydration, and over-the-counter pain relief (as approved by your care team) can help

Constipation: Less common than diarrhea, but reported; increase fiber and fluid intake

In clinical trials, overall adverse reaction rates in patients taking the aprepitant regimen were similar to those in patients receiving standard antiemetic therapy (approximately 69% vs. 68%), suggesting that the side effect burden is not significantly higher than the alternatives.

Serious Side Effects: Call Your Doctor Right Away

Although serious side effects are uncommon, they do occur. Seek emergency medical care or call your oncology team immediately if you experience:

Signs of severe allergic reaction (anaphylaxis): Hives, difficulty breathing, swelling of the face, lips, tongue, or throat. This is a medical emergency—call 911.

Severe skin reactions: Rash with blistering, skin peeling, or sores in the mouth (possible signs of Stevens-Johnson syndrome or toxic epidermal necrolysis—rare but serious). Stop taking Emend and seek care immediately.

Unusual neurological symptoms (if taking ifosfamide): Aprepitant can increase ifosfamide-induced neurotoxicity through CYP3A4 induction. Alert your care team to any confusion, agitation, or behavioral changes if you are receiving ifosfamide-based chemotherapy.

Signs of blood clots (if on warfarin): Emend reduces warfarin levels via CYP2C9 induction, potentially lowering your INR and increasing clotting risk. Watch for unusual bruising, pain or swelling in legs, or shortness of breath.

Severe dizziness or fainting: Blood pressure changes have been reported; notify your team if you feel faint or have significant dizziness.

Special Concerns: Birth Control and Emend

Emend significantly reduces the effectiveness of hormonal birth control, including pills, patches, injections, implants, and vaginal rings. This effect persists for up to 28 days after your last dose. During Emend treatment and for one full month afterward, use a non-hormonal backup method (condom, diaphragm, or spermicide).

This is one of the most commonly overlooked drug interactions with Emend, and your pharmacist and prescriber should counsel you specifically about it before starting.

Side Effects in Pediatric Patients

Clinical trials in pediatric patients showed a similar overall safety profile to adults. However, in pediatric patients receiving ifosfamide chemotherapy, two cases of behavioral changes (agitation and abnormal behavior) were reported in the aprepitant group. Parents and caregivers should monitor for any unexpected behavioral changes and report them immediately.

Managing Common Side Effects at Home

Fatigue: Rest when needed; light activity like short walks can help maintain energy levels

Diarrhea: Stay well-hydrated; avoid high-fiber, greasy, or spicy foods during episodes

Hiccups: Usually resolve on their own; cold water or breathing techniques may provide temporary relief

Appetite loss: Try small, frequent meals; high-calorie, easy-to-eat foods can help maintain nutrition

When to Call Your Doctor vs. When to Go to the ER

Call your oncology team (during business hours or via the after-hours nurse line) for: mild rash, persistent diarrhea or vomiting, unusual bruising, or questions about drug interactions.

Go to the emergency room or call 911 for: difficulty breathing, swelling of the face or throat, blistering rash, or severe chest pain. For a full guide on Emend drug interactions, read our article on Emend drug interactions: what to avoid and what to tell your doctor.