Succinylcholine side effects: definition, risks and contraindications

Anyone planning cosmetic surgery will usually come into contact with the active ingredient succinylcholine without realising it: it is a standard component of the induction of anaesthesia. As the only depolarising muscle relaxant used in human medicine, succinylcholine causes a brief, complete paralysis of the muscles — and comes with a clearly defined profile of side effects. As there is no specific antidote for this active ingredient, it is worth being aware of its risks.

How does succinylcholine work? Mechanism of action and pharmacokinetics

Succinylcholine (suxamethonium) binds to nicotinic acetylcholine receptors on the motor end-plate of skeletal muscle. Acetylcholine is the natural neurotransmitter at this synapse. Succinylcholine mimics its effect but is not broken down by synaptic acetylcholinesterase. The membrane remains permanently depolarised. The muscle fibre is unable to generate any further action potentials and becomes flaccid.

This state persists until the plasma enzyme Pseudocholinesterase (also: butyrylcholine esterase) hydrolyses the active substance. The first breakdown product is succinylmonocholine. Succinylmonocholine binds only weakly to receptors before it breaks down further into succinic acid and choline. Under normal conditions, this breakdown occurs rapidly. Succinylcholine is therefore classified as an ultra-short-acting muscle relaxant.

Why succinylcholine remains clinically indispensable

Succinylcholine is primarily used in rapid sequence induction (RSI). RSI refers to an emergency method of inducing anaesthesia that minimises the risk of aspiration in patients with a full stomach. Its rapid onset of action and short duration of action make succinylcholine the drug of choice for this procedure. If intubation is unsuccessful, the paralysis wears off quickly — allowing the patient to breathe spontaneously again. No non-depolarising muscle relaxant achieves its onset of action within 40–60 seconds as quickly as succinylcholine.

Pseudocholinesterase deficiency: when the effect lasts too long

In cases of genetic or acquired pseudocholinesterase deficiency, the duration of action is significantly prolonged. Typical causes of an acquired deficiency include liver disease, pregnancy, malnutrition or cholinesterase inhibitors. Patients with a severe genetic defect may experience respiratory failure for hours following a standard dose. Mechanical ventilation is then absolutely essential. According to the prescribing information for Succinylcholine 2 % Inresa, a medical history regarding the risk of cholinesterase deficiency must therefore be taken prior to administration.

Succinylcholine side effects: an overview by organ system

The side effects of succinylcholine can be categorised according to the organ systems affected. This categorisation helps the anaesthesia team to identify high-risk patients specifically. The most important categories are explained individually below.

Side effects of succinylcholine by organ system, ranging from common fasciculations to the rare condition of malignant hyperthermia. As at July 2026.

Organ system	Side effect	Prevalence / Risk factor
Skeletal muscles	Fasciculations, post-operative myalgia	Very common (>1 in 10); particularly in muscular patients
Electrolytes / Heart	Hyperkalaemia, cardiac arrhythmias	Occasional (1/100–1/10); dangerous in cases of burns, renal insufficiency or denervation
Cardiovascular	Bradycardia, tachycardia	Occasionally; particularly after repeat doses
Eyes	Increase in intraocular pressure	A well-known effect; of particular concern in cases of glaucoma and penetrating eye injuries
Muscle metabolism	Malignant hyperthermia	Rare (<1>
Immune system	Anaphylaxis / allergic reaction	Rare; in cases of known hypersensitivity
Gastrointestinal tract	Increased intragastric pressure	Due to fasciculations of the abdominal wall muscles

Fasciculations and post-operative myalgia

Fasciculations are brief, uncontrolled muscle twitches. Succinylcholine activates all nicotinic acetylcholine receptors simultaneously. This triggers a synchronous contraction of all muscle fibres. These twitches are visible on the torso, arms and legs. For patients planning cosmetic surgery, this means in practical terms that the twitches are not a sign of a complication, but an expected effect of the anaesthetic.

Fasciculations become problematic because they cause micromechanical damage to the muscle fibres. The effect is similar to a short, intense muscle workout. This results in post-operative myalgia.

Post-operative myalgia: who is most affected?

Post-operative myalgia following succinylcholine manifests as a dull muscle ache. Patients describe it as muscle soreness. The symptoms begin 12–24 hours after the operation. They subside after 1–2 days. Young, physically fit patients experience more severe myalgia than older patients or those with less muscle strength — because their fasciculations are more intense and cause more micro-injuries.

To reduce the effects, the anaesthetic uses a so-called Pre-curation . A subparalytic dose of a non-depolarising muscle relaxant is administered a few minutes before succinylcholine. This occupies some of the acetylcholine receptors and reduces the intensity of fasciculations. However, this measure does not provide complete protection.

Hyperkalaemia: elevated potassium levels as a cardiac risk factor

Hyperkalaemia This is caused by succinylcholine, as the depolarisation of the muscle fibres releases potassium ions from inside the cells into the bloodstream. In healthy patients, the potassium level rises by approximately 0.5 mmol/l. This level does not place a strain on the body.

The situation is different for patients with impaired muscle membrane function or pre-existing hyperkalaemia. According to the product information for Succinylcholine 2 % Inresa, the high-risk groups include:

• Patients with extensive burns (from the second week after the incident)
• Patients with chronic renal failure and pre-existing elevated potassium levels
• Patients with acute or chronic denervation syndromes (e.g. following spinal cord injuries, in cases of severe polyneuropathies)
• Patients following prolonged immobilisation or intensive care

Potassium levels above 6.5 mmol/l lead to serious cardiac arrhythmias. Levels above 7.0 mmol/l can trigger ventricular fibrillation and cardiac arrest. For this reason, a history of hyperkalaemia is considered a relative contraindication. The anaesthesia team will then preferentially choose rocuronium.

Malignant hyperthermia: a rare emergency complication

The malignant hyperthermia (MH) is a rare, potentially fatal pharmacogenetic disorder affecting the skeletal muscles. Succinylcholine and halogenated inhalation anaesthetics such as sevoflurane or isoflurane trigger it in genetically predisposed patients. The mechanism: a defect in the ryanodine receptor (RYR1) leads to uncontrolled calcium release from the sarcoplasmic reticulum of the muscle fibres.

The consequences of this calcium overload are persistent muscle rigidity, an extreme increase in metabolic rate and a rapid rise in temperature to over 40 °C, sometimes as high as 44 °C. At the same time, severe metabolic acidosis develops. The heart responds with tachycardia and arrhythmias.

Symptoms and diagnosis of malignant hyperthermia

Early on, an increase in end-tidal CO₂ (ETCO₂) and tachycardia become apparent — both signs of increased metabolism. Shortly afterwards, muscle rigidity develops, recognisable by increased jaw stiffness (masseter spasm). Without immediate treatment, malignant hyperthermia is life-threatening. The diagnosis is made clinically. A confirmatory test (in vitro contracture test) is only possible postoperatively at specialised centres. In Germany, the German Society for Anaesthesiology and Intensive Care Medicine (DGAI) coordinates these MH reference centres.

Treatment: Dantrolene as a specific antidote

As soon as malignant hyperthermia is detected, the following emergency measures must be taken:

1. Discontinue all triggering factors immediately (succinylcholine, halogenated anaesthetics)
2. Switch to anaesthesia using non-triggering substances (e.g. total intravenous anaesthesia with propofol)
3. Intravenous dantrolene as a specific antidote; dantrolene inhibits the release of calcium from the sarcoplasmic reticulum
4. Physical cooling of the patient (ice packs, chilled infusions)
5. Correction of acidosis and electrolyte imbalances
6. Intensive care monitoring for at least 24 hours

Cardiovascular effects: bradycardia and cardiac arrhythmias

Succinylcholine stimulates not only nicotinic but also muscarinic acetylcholine receptors in the heart. This results in vagal stimulation, which manifests as Bradycardia This effect is particularly pronounced in children and following repeated administration. Paradoxically, tachycardia also occurs in adults when stimulation primarily involves the sympathetic ganglia.

More serious cardiac arrhythmias result from the combination of vagal stimulation and hyperkalaemia. This combination is dangerous in patients with pre-existing conditions. ECG monitoring is therefore mandatory during the administration of succinylcholine.

Increased intraocular pressure: a risk factor in glaucoma and open eye injuries

Succinylcholine increases the following through fasciculations of the extraocular muscles and an increase in central venous pressure: intraocular pressure (IOP) Temporary. In most patients, this effect is clinically insignificant. However, in patients with glaucoma or penetrating eye injuries, increased IOP can cause vitreous humour to be forced out through the wound — with the risk of permanent vision loss.

Succinylcholine is therefore relatively contraindicated in cases of penetrating eye injuries. The decision rests with the experienced anaesthetist, who must weigh up the risk of aspiration (an indication for RSI) against the risk to the eye.

Contraindications: When is succinylcholine unsuitable?

Succinylcholine is not suitable for every patient. The prescribing information for Succinylcholine 2 % Inresa sets out clear absolute and relative contraindications:

1. Absolute contraindication: a history of malignant hyperthermia or a family history of the condition
2. Absolute contraindication: lack of facilities for artificial ventilation
3. Relative contraindication: Pseudocholinesterase deficiency (prolonged neuromuscular blockade)
4. Relative contraindication: Risk of hyperkalaemia (burns from the second week onwards, renal insufficiency, denervation syndromes)
5. Relative contraindication: Glaucoma or penetrating eye injuries
6. Relative contraindication: neuromuscular disorders (e.g. muscular dystrophies, myasthenia gravis)
7. Relative contraindication: known hypersensitivity to other muscle relaxants

According to the product information, succinylcholine must only be administered by doctors who are proficient in intubation, artificial ventilation and resuscitation procedures. Neuromuscular function should be monitored intraoperatively using a Nerve stimulators be monitored to prevent overdoses and underdoses.

Succinylcholine vs. Rocuronium: Comparison and Decision-Making Criteria

Succinylcholine and rocuronium are the two muscle relaxants primarily used for RSI. Both have different profiles of side effects. The following table summarises the key differences:

Characteristic	Succinylcholine	Rocuronium
Class of active substances	Depolarising muscle relaxant	Non-depolarising muscle relaxant
Onset of action (i.v.)	40–60 seconds	60–90 seconds (at 1.2 mg/kg: approx. 60 sec.)
Duration of action	4–6 minutes	30–60 minutes (depending on the dose)
Can be antagonised	No	Yes, completely with sugammadex
Risk of hyperkalaemia	Yes	No
Malignant hyperthermia	Trigger	No trigger
Fasciculations	Yes	No
Benefit for RSI	Shortest duration of action in the event of intubation failure	Reversible with sugammadex

The availability of Sugammadex, a cyclodextrin derivative that selectively binds to and neutralises rocuronium, has transformed the clinical debate. Should a „Cannot Intubate, Cannot Oxygenate“ situation arise, sugammadex completely reverses the neuromuscular blockade in approximately 3 minutes. This represents a significant safety advantage over succinylcholine, which cannot be antagonised.

Nevertheless, succinylcholine remains the preferred choice in certain situations: in patients with no contraindications, when the shortest possible duration of action is crucial, or when sugammadex is not available.

Anaesthetic complications in cosmetic surgery: financial protection

Cosmetic surgery such as liposuction, tummy tucks or rhinoplasty is almost always carried out under general anaesthesia. This involves the use of muscle relaxants such as succinylcholine. Anaesthetic complications are rare, but can occur — through no fault of either the doctor or the patient.

If a complication arises following a cosmetic procedure, statutory health insurance funds will only cover some of the resulting costs, if any at all. Treatments, revision surgery and hospital stays must then be paid for privately. Such costs can quickly mount up to substantial sums.

One Consequential Costs Insurance covers you in precisely this situation: it covers medically necessary follow-up treatment and operations resulting from the insured procedure — transparently and without any red tape. You can find further information on the terms and conditions and the procedures covered in our FAQ section.

Frequently Asked Questions about the side effects of succinylcholine