Terrell (Isoflurane) Side Effects: What to Expect and When to Call Your Doctor

If you're scheduled for surgery and you know you'll be receiving general anesthesia — or if you've recently had a procedure where Terrell (isoflurane) was used — you might be wondering about side effects. What's normal after waking up from anesthesia? What requires a call to your doctor? And what are the rare but serious reactions to watch for?

This guide covers the full side effect profile of Terrell (isoflurane) in plain language, so you know what to expect.

Most Common Side Effects of Terrell (Incidence Greater Than 5%)

The following side effects were reported in more than 5% of patients in clinical trials of isoflurane:

• Agitation: Restlessness, confusion, or temporary agitation during emergence from anesthesia is very common. This usually resolves within minutes to hours.
• Cough and breath holding: Isoflurane has a mildly pungent odor that can irritate the airways during induction, causing coughing or brief breath holding.
• Nausea and vomiting: Post-operative nausea and vomiting (PONV) is a well-known side effect of all inhalational anesthetics. Your anesthesia team will often give anti-nausea medications proactively.
• Chills and shivering: Post-anesthesia shivering is common, particularly as your body temperature normalizes after surgery. Warming blankets and specific medications (like meperidine in low doses) can help.
• Laryngospasm: An involuntary spasm of the vocal cords. This is more likely during induction and is managed immediately by the anesthesia team.
• Delirium: Temporary confusion after surgery, especially in older patients. This typically clears within hours to days.

Cognitive Effects: Temporary Mental Fuzziness After Surgery

Terrell's prescribing information notes that general anesthetics — including isoflurane — may cause a slight decrease in intellectual function for 2–3 days following anesthesia. Small mood changes may also persist for up to 6 days. This is normal and expected. You should not drive, make major financial decisions, or sign legal documents for at least 24 hours after receiving general anesthesia.

Serious Side Effects: Know the Warning Signs

While rare, some side effects of Terrell are serious and require immediate medical attention:

• Malignant hyperthermia (MH): A potentially fatal reaction to halogenated anesthetics (and succinylcholine) in genetically susceptible individuals. Symptoms include rapidly rising body temperature, fast heartbeat, fast breathing, muscle rigidity, and dark urine. MH is a medical emergency — call 911 or go to the ER immediately.
• Hepatotoxicity (liver problems): Very bad and sometimes fatal liver problems have been reported with isoflurane. If you develop dark urine, yellow skin or eyes (jaundice), persistent fatigue, nausea, or loss of appetite in the days to weeks following surgery, contact your doctor immediately.
• Perioperative hyperkalemia: Elevated potassium levels can rarely occur, particularly in children with underlying muscle conditions (like Duchenne muscular dystrophy). This can cause dangerous heart rhythm problems.
• QT prolongation: Terrell can rarely cause QT prolongation on ECG, which can lead to serious heart rhythm problems. This is monitored during surgery.

Pediatric Special Concerns

Parents of young children should know:

• Neurodevelopmental concerns: Studies in young animals and children suggest that repeated or prolonged use of anesthetic drugs in children younger than 3 years may have negative effects on brain development. The FDA requires all general anesthetics to carry this warning. Discuss the timing of elective procedures with your child's pediatrician and surgical team.
• Emergence agitation in children: Young children often experience a brief but intense period of agitation or crying when waking from anesthesia. This is typically short-lived and not harmful.

When to Call Your Doctor After Surgery

Contact your surgeon or anesthesia provider if you experience any of the following after your procedure:

• Persistent or severe nausea and vomiting (beyond 24 hours)
• Yellowing of the skin or whites of the eyes (jaundice)
• Dark (tea-colored) urine
• Prolonged confusion, disorientation, or unusual behavior beyond 24 hours
• High fever, rapid heartbeat, or muscle stiffness (seek emergency care immediately — possible MH reaction)

If you need to find anti-nausea medications, pain relievers, or other post-surgical prescriptions at a pharmacy near you, medfinder can help you locate them quickly.

Also read: Terrell drug interactions: what to avoid and tell your doctor.