Understand prolonged muscle paralysis, malignant hyperthermia, and what a genetic result can add to your anesthesia plan.
Genetic differences can affect how your body responds to some medicines used during anesthesia. Two findings have different explanations: reduced BCHE enzyme activity can make certain muscle relaxants last longer, while specific RYR1 or CACNA1S variants can increase susceptibility to malignant hyperthermia, a serious reaction to certain anesthetic drugs.[1][2]
| Genetic finding | Medicines affected | What it can mean |
|---|---|---|
| Reduced BCHE activity | Succinylcholine and mivacurium. | Muscle paralysis can last longer than expected, including weakness of the muscles needed to breathe.[1] |
| RYR1 / CACNA1S susceptibility | Triggering volatile anesthetics, such as sevoflurane, and succinylcholine. | Risk of malignant hyperthermia. CPIC recommends an anesthesia plan that avoids triggering drugs when a qualifying susceptibility variant is present.[2] |
The BCHE gene helps your body make butyrylcholinesterase, also called pseudocholinesterase. This enzyme circulates in the blood and breaks down succinylcholine and mivacurium. These drugs temporarily prevent muscles from moving, including the muscles used for breathing.[1]
When the enzyme works poorly, the drugs can remain active for longer. In severe deficiency, breathing support may be needed for hours while the effect wears off. This is called prolonged neuromuscular blockade. It is distinct from malignant hyperthermia.[3]
The degree of reduced activity matters. An intermediate metabolizer result is different from a poor metabolizer result. For succinylcholine, the FDA advises avoiding use in poor metabolizers and describes clinician-administered sensitivity testing and cautious administration for patients with reduced metabolism. The result should be reviewed with the anesthesia team, who can choose an alternative drug or an appropriate management plan.[4]
A DNA result does not directly measure enzyme activity. Pregnancy, some illnesses, and medicines can also lower activity. If your history suggests a problem, a clinician may request an enzyme activity measurement and a dibucaine test, which helps identify certain forms of the enzyme.[1][3]
RYR1 and CACNA1S help control calcium signaling in skeletal muscle. Certain disease-causing variants can allow a triggering anesthetic to provoke uncontrolled muscle activity. The resulting malignant hyperthermia (MH) reaction can cause muscle rigidity, rapidly rising carbon dioxide, overheating, and muscle breakdown. It is a medical emergency.[2]
A susceptibility finding means an increased risk if a triggering drug is used; it does not mean an MH reaction is happening now. Not every variant in these genes causes susceptibility. Clinical interpretation of the specific variant matters.[2]
Having had anesthesia before without a problem does not rule out MH susceptibility. A person may have an uneventful exposure and still react on another occasion. Personal and family history remain relevant even when a genetic test has not identified a cause.[5]
The MH-triggering group includes the volatile anesthetics sevoflurane, desflurane, isoflurane, enflurane, halothane, and methoxyflurane, as well as succinylcholine. Volatile agents are delivered through the breathing system. Succinylcholine is a muscle relaxant.[6]
Succinylcholine appears in both genetic risk groups for different reasons: reduced BCHE activity can prolong its muscle-blocking effect, while MH susceptibility concerns a separate reaction. Mivacurium does not trigger MH, but reduced BCHE activity can still prolong its effect.[4][6]
There are non-triggering options for people susceptible to MH. MHAUS lists propofol, nitrous oxide, local anesthetics, and muscle relaxants such as rocuronium as non-triggering. This describes their relationship to MH, not their suitability for every patient or every procedure. The anesthesia team chooses the drugs and monitoring needed for your situation.[6]
Known or suspected MH susceptibility does not automatically prevent surgery. MHAUS describes how care can proceed with non-triggering anesthesia at an appropriately prepared facility, including when diagnostic testing has not yet been completed.[7]
The Gene2Rx Full Report assesses BCHE for supported genotyping-array and whole-genome sequencing (WGS) uploads. Its targeted RYR1/CACNA1S assessment requires eligible original WGS data. Consumer array data cannot provide a negative MH result. Explore Full Report coverage.
The MH screen checks a defined list of susceptibility variants. It does not interpret every possible variant in these genes. An absent site in a variant file also does not, by itself, establish that the site was adequately sequenced.
A normal BCHE result does not establish that someone is free of MH susceptibility, and an MH result does not measure BCHE activity. These are separate assessments.
If a personal or family history raises concern, specialist evaluation can go beyond a targeted screen. MH diagnostic options include clinical genetic testing and a muscle biopsy contracture test; MHAUS recommends discussing the appropriate test with a genetic counselor.[8]
Bring the actual report and any records of a previous reaction to the pre-anesthesia assessment. Details such as the medicines given and the treatment required are more useful than a general description like “anesthesia did not agree with me.”
Tell the team about:
Useful questions include: Does this result change the anesthesia plan? Is confirmatory testing or specialist review needed? How should the finding be recorded for future care? If an inherited susceptibility is confirmed, ask whether relatives should be offered evaluation.[5]
Planning ahead lets the anesthesia team consider your history, procedure, medicines, and genetic findings together. The aim is an appropriate plan for your care, not a universal list of drugs you should choose for yourself.
Explore each medication's genetic findings, supporting sources, and report information.
Combined products and brand names for the medications above. Each links to a pharmacogenetic breakdown.
The Full Report includes BCHE assessment for supported uploads and targeted RYR1/CACNA1S screening for eligible original WGS. Review the findings and their limits with your anesthesia team.
Get your report Look up a medicationInformational only, not medical advice. Pharmacogenetic guidelines describe population-level patterns that inform prescribing decisions. Never start, stop, or change a medication without talking to your prescribing clinician.