Paralytic Drugs Explained

A paralytic, also described as a neuromuscular blocking agent, is a type of powerful muscle relaxant used to prevent muscle movement during surgical procedures or during critical care for severe respiratory illnesses.

Your anesthesiologist would administer a paralytic into your intravenous line (IV, in a vein) before and during your procedure and would monitor the effects throughout your surgery.

When these medications are used during critical care, they are usually used for a longer time period than when they are used during surgery.

Why Paralytics Are Used

Paralytics are used as part of general anesthesia, to prevent movement during surgery. General anesthesia involves medications that put you to sleep and prevent pain, like ketamine, as well as muscle paralytics to prevent movement.

Because surgery uses sharp instruments and affects delicate areas of the body, even involuntary movements, such as a sneeze or a small muscle twitch, could cause a serious injury. For this reason, muscle movement has to be medically suppressed during surgery, with the exception of the muscle movement that's necessary for breathing. 

Critical Care

Sometimes neuromuscular blocking agents are used during intensive care for severe respiratory distress syndrome when a person requires intubation (insertion of a breathing tube in the throat) due to impaired breathing.

In these situations, muscle paralysis is usually maintained for 12 to 24 hours or longer.

How Paralytic Drugs Work

Paralytic drugs temporarily interfere with the messages that nerves send to the skeletal muscles of the body. The skeletal muscles are those that control movements of the face, arms, legs, back, and trunk.

The muscles of the diaphragm, which help expand the lungs, are also paralyzed by these medications. While under the effect of a neuromuscular blocking agent, you would need mechanical assistance to help you breathe because diaphragmatic muscle paralysis prevents you from breathing on your own. A breathing tube and ventilator will be needed to help you breathe. 

Paralytic drugs are rapidly distributed throughout the body after they are injected. They quickly bind to and block neuromuscular binding sites on muscles to prevent them from functioning.

These drugs can affect people differently. For example, they may take longer to work in adults over age 80, or their action can last longer for people who have kidney or liver disease.

Most Commonly Used Paralytic Drugs

Paralytic drugs are available in hospitals and surgical facilities. Your dose would be carefully selected before it is started, and you need to be closely monitored if you receive any of these medications.

Succinylcholine, a rapid-onset, short-acting depolarizing muscle relaxant, has traditionally been the drug of choice when rapid muscle relaxation is needed.

Common paralytics used for surgery include:

• Succinylcholine
• Rocuronium
• Vecuronium
• Mivacurium
• Atracurium
• Cisatracurium

When surgery is complete, medication is given to reverse the effects of the paralytic drugs. Examples include acetylcholinesterase inhibitors, neostigmine, and edrophonium. As with paralytic drugs, the dosage must be carefully selected to avoid negative side effects.

What Paralytics Don't Do

General anesthesia involves a combination of medications, monitoring, and support. Paralytics are one part of the whole general anesthesia process, and they do not impact pain or memory. Other anesthetic medications provide sedation (put you to sleep) and pain control.

Sedation that's given for surgery also prevents people from remembering the surgery, as well as aspects of the immediate pre-operative and post-operative period.

Local Anesthesia

Neuromuscular blocking agents are different from local anesthetics that are injected to prevent pain in a small region of your body. Local anesthetics used for surgery might be injected while you are awake—such as during dermatologic procedures, some types of limb surgeries, and more.

Home Use

Neuromuscular blocking agents are not used at home. Some milder muscle relaxants, like Flexeril (cyclobenzaprine), are taken orally or injected for problems like muscle spasms or pain, but they are not as powerful as neuromuscular blocking agents that are used for surgery.

Paralytic Drugs Side Effects

Even with appropriate use and careful monitoring, neuromuscular blocking agents can cause side effects.

Common Side Effects

Some common side effects of neuromuscular blocking agents include:

• Muscle twitching
• Altered heartbeat
• Rapid or slowed breathing
• Increased body temperature
• Blood pressure changes

During surgery, you would be monitored so that your anesthesiologist would be able to detect these side effects quickly. Treatment would be initiated right away so that your surgery can proceed safely.

Severe Side Effects

Serious side effects of neuromuscular blocking agents can include:

• Respiratory arrest
• Heart attack
• Muscle breakdown

Severe complications are more common among people who are at high risk due to heart disease, lung disease, obesity, or neuromuscular disease. Part of your pre-surgical testing involves identifying potential predisposing factors that could put you at an increased risk of anesthesia side effects, and potentially adjusting your anesthesia dosing in advance to avoid adverse effects.