Acetaminophen/Caffeine Side Effects: What to Expect and When to Call Your Doctor

Acetaminophen/caffeine (found in Excedrin Tension Headache, Excedrin Mild Headache, and generics) is generally well-tolerated when used as directed. But like all medications, it can cause side effects — some minor and manageable, others serious enough to require immediate attention. Here's what you need to know.

Common Side Effects of Acetaminophen/Caffeine

Most people tolerate this combination well, but caffeine in particular can cause noticeable stimulant effects:

• Nervousness or anxiety: Caffeine is a stimulant. Sensitive individuals may feel jittery or anxious, especially at higher doses or when combined with other caffeine sources.
• Insomnia or trouble sleeping: Do not take acetaminophen/caffeine close to bedtime. The 65 mg caffeine per tablet is roughly equivalent to a half cup of coffee and can interfere with sleep.
• Rapid or irregular heartbeat: Caffeine can cause palpitations in some people, especially those with underlying heart conditions or who are sensitive to stimulants.
• Irritability: As caffeine wears off, some people experience irritability or mood changes, especially with regular use.
• Nausea or upset stomach: Acetaminophen rarely causes stomach upset on its own, but caffeine can irritate the stomach lining in some individuals. Taking the tablet with food or milk may help.
• Headache on overuse: Using caffeine-containing pain relievers more than 10 days per month can cause medication-overuse headache (MOH), a condition where the medication begins triggering the headaches it's meant to treat.

Serious Side Effects: When to Stop and Call Your Doctor

Stop using acetaminophen/caffeine and contact your doctor or seek emergency care if you experience any of the following:

• Signs of liver damage: Nausea, severe upper stomach pain, loss of appetite, dark urine, clay-colored stools, or yellowing of the skin or eyes (jaundice). This is the most serious risk of acetaminophen overdose or overuse.
• Severe skin reactions: Stevens-Johnson syndrome and toxic epidermal necrolysis are rare but potentially fatal reactions to acetaminophen. Symptoms include skin reddening, blistering, or a rash that spreads. If this occurs, stop the medication immediately and seek emergency care.
• Allergic reaction: Hives, swelling of the face or throat, difficulty breathing, or shock. Seek emergency care (call 911) immediately.
• Chest pain or severe palpitations: Caffeine can exacerbate cardiac arrhythmias. If you experience chest pain, a racing heartbeat, or feel faint after taking this medication, stop and seek care.

The Liver Warning: How Much Acetaminophen Is Too Much?

This is the most important safety consideration for acetaminophen/caffeine. The maximum safe dose of acetaminophen for healthy adults is 4,000 mg per day (lower for those with liver disease or who drink alcohol regularly — 2,000-3,000 mg/day).

Each tablet of Excedrin Tension Headache contains 500 mg of acetaminophen. If you take the maximum recommended dose of 2 tablets every 6 hours (8 tablets/day), that's 4,000 mg of acetaminophen — the maximum limit. You must NOT take any other acetaminophen-containing medication (Tylenol, NyQuil, Percocet, etc.) on the same day.

Acetaminophen is hidden in hundreds of OTC and prescription products. Always read labels carefully before combining medications.

Caffeine Withdrawal: What Happens If You Stop Suddenly?

If you've been taking acetaminophen/caffeine frequently, stopping abruptly can cause caffeine withdrawal symptoms, including: headache (a rebound headache), fatigue, irritability, and difficulty concentrating. These symptoms typically resolve within 2-9 days. If you experience withdrawal headaches when you stop, talk to your doctor rather than resuming the medication — this may indicate medication dependency.

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Who Should Be Extra Careful With This Medication?

• People with liver disease or who drink 3+ alcoholic beverages daily — increased risk of liver damage
• People on warfarin — acetaminophen can enhance the blood-thinning effect
• People with anxiety disorders or insomnia — caffeine may worsen symptoms
• Pregnant women — limit caffeine to under 200 mg/day total; consult OB before use
• Children and teenagers — consult a doctor; the caffeine component may not be appropriate for all ages

Need Help Finding This Medication?

If you're looking for acetaminophen/caffeine at a pharmacy near you, medfinder calls pharmacies and texts you results. Also see our related guide: Acetaminophen/Caffeine Drug Interactions: What to Avoid.