Midazolam

Midazolam is a water-soluble benzodiazepine used for seizure control, sedation and balanced anesthesia. It is frequently combined with other sedatives or anesthetics to provide muscle relaxation and reduce the amount of accompanying drugs required. Its injectable formulation also supports nonintravenous seizure-rescue applications in selected veterinary patients.

Group

Benzodiazepine sedative and anticonvulsant

Mechanism of Action

Midazolam acts as a positive allosteric modulator at benzodiazepine-sensitive GABA-A receptor complexes. In the presence of GABA, it increases the frequency of chloride-channel opening and strengthens inhibitory neurotransmission. Reduced neuronal excitability produces anticonvulsant effects, while action in other central pathways contributes to sedation, anxiolysis and muscle relaxation.

Dose Rates

Dogs

Use / stage	Dose	Route	Schedule	Instructions
Sedation or anaesthetic adjunct	0.1–0.25 mg/kg	IV, IM
Sedative infusion	0.1–0.3 mg/kg/hour	IV	Continuous
Status epilepticus	0.1–0.2 mg/kg	IV	Once
Status epilepticus	0.2 mg/kg	IN	Once	5 mg/mL solution; nasal rescue route.
Oral sedation	0.5–0.75 mg/kg	PO		2 mg/mL syrup; extrapolated from paediatric use rather than established veterinary efficacy.
Opioid-associated premedication	0.2–0.4 mg/kg	IV, IM		With an appropriate opioid; hydromorphone examples are 0.1 mg/kg IV or 0.2 mg/kg IM.
Status epilepticus	0.07–0.2 mg/kg	IV, IM		Short effect; transition to a monitored infusion if seizures recur.
Status-epilepticus infusion	0.05–0.5 mg/kg/hour	IV	Continuous
IV anaesthetic adjunct	0.1–0.5 mg/kg	IV
Status epilepticus	0.25 mg/kg	IV	Once

Cats

Use / stage	Dose	Route	Schedule	Instructions
Sedation	0.05 mg/kg	IV
Ketamine-associated induction	Reference only	IV		Midazolam 0.3-0.6 mg/kg with ketamine 3 mg/kg IV; additional ketamine 1-2 mg/kg may be used as needed. A combination protocol is required.
Opioid-associated premedication	0.2–0.4 mg/kg	IV, IM		With an appropriate opioid; hydromorphone examples are 0.1 mg/kg IV or 0.2 mg/kg IM.
Status epilepticus	0.07–0.2 mg/kg	IV, IM		Short effect; transition to a monitored infusion if seizures recur.
Status-epilepticus infusion	0.05–0.5 mg/kg/hour	IV	Continuous
IV anaesthetic adjunct	0.1–0.5 mg/kg	IV

Pigs

Use / stage	Dose	Route	Schedule	Instructions
Sedation or anaesthetic adjunct	0.5 mg/kg	IM		Reported upper dose; usually combined with ketamine, not evidence of a lower endpoint.

Horses

Use / stage	Dose	Route	Instructions
Neonatal seizures — Loading	0.1–0.2 mg/kg	IV, IM	Foals only. IV delivery over 15-20 minutes; the fixed 5-10 mg example is not a universal dose.
Neonatal seizure infusion	Reference only	IV	Reported guidance states 3 mg/hour IV after loading, but the accompanying 2-6 mL/hour range and nominal 0.5 mg/mL mixture do not define a consistent patient-specific rate. A fixed mg/hour infusion requires a patient-specific delivery plan.
Anaesthetic induction adjunct	Reference only	IV	Midazolam 0.1 mg/kg with ketamine 2.2 mg/kg IV and appropriate sedative premedication; not a stand-alone anaesthetic regimen.
Neonatal seizure example	Reference only	IV	For a 50 kg foal: 2-5 mg IV; CRI example 1-3 mg/hour. This remains a weight-qualified patient example, not a universal fixed foal dose. Rapid IV administration can cause apnoea and hypotension.
Neonatal seizure example	Reference only	IM	For a 50 kg foal: 2-5 mg IM, repeated only to effect; do not infer a general dose from the example weight.

Sheep

Use / stage	Dose	Route	Schedule	Instructions
Short-term sedation	0.5 mg/kg	IV, IM

Rabbits

Use / stage	Dose	Route	Instructions
Sedation adjunct	1–2 mg/kg	IM, IV
Preanaesthetic anxiolysis	0.5–5 mg/kg	IM, IV
Titrated IV induction adjunct	0.05–0.5 mg/kg	IV	Preoxygenate and provide intubation/ventilation; administer to effect, especially after fentanyl.

Mice

Use / stage	Dose	Route	Schedule	Instructions
Preanaesthetic anxiolysis	3–5 mg/kg	IM, IV
Sedation adjunct	1–2 mg/kg	IM

Rats

Use / stage	Dose	Route	Schedule	Instructions
Preanaesthetic anxiolysis	3–5 mg/kg	IM, IV
Sedation adjunct	1–2 mg/kg	IM

Gerbils

Use / stage	Dose	Route	Schedule	Instructions
Preanaesthetic anxiolysis	3–5 mg/kg	IM, IV
Sedation adjunct	1–2 mg/kg	IM

Hamsters

Use / stage	Dose	Route	Schedule	Instructions
Preanaesthetic anxiolysis	3–5 mg/kg	IM, IV
Sedation adjunct	1–2 mg/kg	IM

Guinea pigs

Use / stage	Dose	Route	Schedule	Instructions
Preanaesthetic anxiolysis	3–5 mg/kg	IM, IV
Sedation adjunct	1–2 mg/kg	IM

Chinchillas

Use / stage	Dose	Route	Schedule	Instructions
Preanaesthetic anxiolysis	3–5 mg/kg	IM, IV
Sedation adjunct	1–2 mg/kg	IM

Birds

Use / stage	Dose	Route	Schedule	Instructions
Analgesia-associated sedation	1–2 mg/kg	IM, IV		With a suitable analgesic; midazolam itself is not adequate analgesia.
Stress-reduction premedication	1 mg/kg	IM		Higher doses up to 6 mg/kg are described but require species- and procedure-specific titration.

Indications

Emergency treatment of seizures, cluster seizures and status epilepticus in dogs and cats.
Control of selected neonatal seizures, including seizures in foals.
Preanesthetic medication and co-induction of general anesthesia in veterinary patients.
Adjunctive sedation and muscle relaxation during diagnostic or surgical procedures.
Continued anticonvulsant or sedative support by infusion in selected critical-care patients.

Contraindications

Use cautiously with respiratory compromise, opioids or glaucoma.
Prolonged administration should be tapered.

Interactions

Other sedatives and opioids increase cardiorespiratory depression.
Azole antifungals such as ketoconazole can inhibit clearance.

Adverse effects

Sedation, ataxia and paradoxical excitement
Serious respiratory or cardiovascular depression after rapid IV administration
Equine weakness and agitation

Toxicity

Support ventilation and circulation; flumazenil may reverse severe benzodiazepine effects but requires assessment of seizure and dependence risks.

Preparations

Preparation	Form	Strength	Route
Midazolam 5 mg/mL injection	Injection	5 mg / mL	IV, IM, IN
Midazolam 2 mg/mL oral syrup	Oral Liquid	2 mg / mL	PO
Nayzilam 5 mg/0.1 mL nasal spray Human single-dose nasal product; amount is per 0.1 mL, not per mL. Not automatically interchangeable with a measured veterinary nasal rescue volume.	Other	5 mg / 0.1 mL	IN
Midazolam 1 mg/mL injection	Injection	1 mg / mL	IV, IM

Monitoring and Administration

Give IV doses slowly and monitor respiration and blood pressure.

Acidic pH maintains solubility. Compatible water-soluble anaesthetics may be mixed immediately before administration, but storage compatibility must not be assumed.

The described foal infusion recipe adds 50 mg to 100 mL saline and calls the final concentration 0.5 mg/mL; added drug volume changes the final volume, so do not use this as a verified final concentration.

The equine preoperative range printed as 0.011-0.0.44 mg/kg IV has a malformed upper endpoint and is not repaired by guessing. The 50:50 ketamine/midazolam volume mixture assumes exact concentrations: 1 mL/9.1 kg is described as about 0.28 mg/kg midazolam plus 5.5 mg/kg ketamine; no route is supplied for that mixture entry. Bird combination ketamine 10-30 mg/kg plus midazolam 2-6 mg/kg requires an independently defined administration route and analgesia plan.