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

Starting Temodar (temozolomide) can feel overwhelming when you read through the list of potential side effects. The good news: many patients tolerate temozolomide reasonably well, and most common side effects can be managed with supportive care. The key is knowing what's expected, what's serious, and when to call your care team.

Common Side Effects of Temodar

These side effects are frequently reported and generally manageable:

Nausea and vomiting: One of the most common side effects. Taking temozolomide on an empty stomach or at bedtime may help reduce nausea. Anti-nausea medications (antiemetics) are often prescribed prophylactically.

Fatigue: Cancer-related fatigue is common during chemotherapy. Plan rest and prioritize activities. Light exercise, if medically appropriate, can help.

Hair loss (alopecia): Hair loss typically occurs during treatment and often grows back after chemotherapy ends. Note: hair loss from radiation to the scalp may be permanent in the treated area.

Constipation: Common, especially when combined with anti-nausea medications (many antiemetics cause constipation). Stool softeners and dietary fiber can help.

Headache: Can be related to the cancer itself, corticosteroids (often used alongside chemoradiation), or the chemotherapy. Report persistent or worsening headaches to your team.

Decreased appetite: Poor appetite is common during treatment. Work with a dietitian if nutritional intake becomes a concern.

Dizziness and coordination problems: May result from the brain tumor, radiation, or temozolomide. Report new or worsening neurological symptoms promptly.

Serious Side Effects: Call Your Doctor Immediately

Some side effects of temozolomide are serious or life-threatening and require immediate medical attention:

Myelosuppression (low blood cell counts): Temozolomide can cause dangerously low white blood cells (neutropenia), platelets (thrombocytopenia), and red blood cells (anemia). Signs include fever, unusual bruising or bleeding, and extreme fatigue. Blood counts must be monitored before every cycle.

Serious infections: Low white blood cells increase infection risk, including a life-threatening lung infection called Pneumocystis pneumonia (PCP). Fever of 100.4°F or higher during treatment is a medical emergency — call your oncology team immediately.

Liver toxicity (hepatotoxicity): Temozolomide can cause liver enzyme elevations and, in rare cases, serious or fatal liver damage. Warning signs include yellowing of the skin or eyes (jaundice), abdominal pain, or dark urine. Liver function tests are monitored regularly during treatment.

Aplastic anemia: A rare but potentially fatal blood condition where bone marrow fails to produce enough blood cells. Prolonged pancytopenia has been reported, including fatal cases.

Pulmonary toxicity: Rare but serious lung reactions including interstitial pneumonitis and pulmonary fibrosis have been reported. Signs include new cough, shortness of breath, and fever.

Severe allergic reactions: Anaphylaxis, Stevens-Johnson syndrome, and toxic epidermal necrolysis have been reported. Seek emergency care immediately for difficulty breathing, severe rash, or skin peeling.

Monitoring Required During Temodar Treatment

Your oncology team will schedule regular monitoring to catch side effects early:

Complete blood count (CBC) with differential — before every cycle, and more frequently during concurrent phase

Liver function tests (LFTs) — periodically during treatment and following the last dose

MRI brain scans — typically every 2–3 cycles to monitor tumor response

Tips for Managing Common Side Effects

Take temozolomide at bedtime on an empty stomach to minimize nausea

Take anti-nausea medication as prescribed — don't wait until you feel sick

Swallow capsules whole — never open, chew, or crush them (the powder is hazardous)

Wash hands thoroughly after handling capsules; avoid contact with skin, eyes, or mucous membranes

Avoid people with infections when your blood counts are at their lowest (typically 21–28 days after dosing)

Also read: Temodar Drug Interactions: What to Avoid and What to Tell Your Doctor

If you're having trouble locating your Temodar prescription, medfinder can help find which pharmacies near you can fill it.