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

Midazolam is a powerful central nervous system depressant, and understanding its side effect profile is essential for patients and caregivers — whether it's been administered before a procedure, prescribed as Nayzilam for seizure rescue, or given as a continuous ICU infusion. Here's what to expect, what to watch for, and when to seek immediate medical attention.

Boxed Warning: Respiratory Depression

Midazolam carries a black box warning — the FDA's most serious warning level — regarding the risk of respiratory depression, airway obstruction, and cardiac arrest. This risk is highest when:

Midazolam is given rapidly intravenously

It is used concurrently with opioids (fentanyl, morphine, oxycodone) or other CNS depressants

It is given to elderly patients, debilitated patients, or those with breathing problems such as COPD

For this reason, injectable midazolam must only be administered in monitored clinical settings where resuscitative equipment and trained personnel are immediately available.

Common Side Effects of Midazolam

Most patients experience some or all of these expected effects — they are part of how midazolam works:

Drowsiness and sedation: You may feel very sleepy for several hours after receiving midazolam. Plan for someone to drive you home and monitor you if you're having an outpatient procedure.

Memory loss (anterograde amnesia): Midazolam produces amnesia for events during and after administration. You may not remember your procedure or the recovery room — this is expected and temporary.

Dizziness and coordination problems: Don't drive or operate machinery until the effects have fully worn off — at least 24 hours after the dose.

Nausea and vomiting: Common after procedural use, especially when combined with opioids

Headache: Mild headache is common, particularly after intranasal use (Nayzilam)

Nasal irritation (Nayzilam): Nasal discomfort, throat irritation, runny nose, and altered taste are common with intranasal administration

Pain or redness at injection site: Common with IV or IM administration

Hiccups: Occasionally reported after IV or IM injection

Serious Side Effects — Seek Emergency Care Immediately

Slow, shallow, or stopped breathing (respiratory depression): Call 911 immediately. This is the most dangerous side effect and can be fatal.

Loss of consciousness: Unresponsiveness or failure to wake after expected recovery time — call 911

Extreme agitation or paradoxical reaction: Some patients — particularly children and elderly individuals — experience paradoxical excitement, agitation, involuntary movements, or combativeness instead of sedation

Severe hypotension (low blood pressure): Lightheadedness, fainting, rapid heart rate in monitored settings

Signs of allergic reaction: Hives, difficulty breathing, swelling of face or throat — call 911

Special Populations: Who Needs Extra Caution?

Elderly patients: Metabolize benzodiazepines more slowly; require reduced doses and longer monitoring periods

Neonates: Should not receive rapid IV bolus midazolam; risk of severe hypotension and neurological injury; maximum 72-hour limit in NICUs

Pregnant women: Risk of neonatal withdrawal if used late in pregnancy; discuss risks and benefits with your provider

Patients with liver or kidney disease: Reduced elimination leads to prolonged effects; dose reduction required

Patients with glaucoma: Contraindicated in acute narrow-angle glaucoma; caution in open-angle glaucoma

Nayzilam-Specific Side Effects

The most common side effects specifically associated with Nayzilam nasal spray include somnolence (sleepiness), headache, nasal discomfort, throat irritation, and rhinorrhea (runny nose). These local effects are typically short-lived and resolve within the same day. Serious effects including respiratory depression can still occur and should be treated as emergencies.

For information on what medications interact with midazolam, see: Midazolam Drug Interactions: What to Avoid and What to Tell Your Doctor.