Methoxyflurane, Genetics, and Malignant Hyperthermia
Methoxyflurane is included among the volatile agents covered by CPIC malignant hyperthermia guidance. Its use and formulation can differ by country and clinical setting; the exact product should be discussed with the treating clinician.
How muscle calcium signaling connects to anesthesia
Muscle cells release and store calcium to coordinate contraction. RYR1 forms a calcium-release channel; CACNA1S helps couple the electrical signal to that release. Certain variants make this system vulnerable to an uncontrolled response when a triggering anesthetic is given. The resulting malignant hyperthermia reaction can involve muscle rigidity, rising carbon dioxide, and dangerous overheating. [1]
CPIC recommends avoiding triggering anesthetics when a qualifying susceptibility variant is present. This is an anesthesia-selection issue, rather than a recommendation to simply lower the dose. The anesthesia team can plan an approach using non-triggering agents. [1]
Reading the anesthesia finding in your report
| Report finding | How to use it |
|---|---|
| Susceptibility finding | Bring the result to the anesthesia team before a procedure. They can review the variant, confirm its clinical interpretation, and plan care. |
| No listed variant detected | None of the variants covered by this screen was identified. Other genetic causes and your personal or family history still matter. |
| Unable to determine | The supplied data did not support a reliable interpretation. This is not a negative result. |
| Not assessed | This assessment was not available for the report or uploaded data. Consumer array reports do not include the targeted RYR1/CACNA1S screen. |
The succinylcholine and mivacurium findings involving BCHE answer a different question: prolonged muscle relaxation. A BCHE result does not establish malignant hyperthermia susceptibility.
Preparing for a conversation with your anesthesia team
Keep a copy of your genetic report with records of any previous anesthesia reaction. If a relative had an unexplained reaction during surgery, mention it when your procedure is being planned. Useful questions are whether your history warrants specialist evaluation, whether confirmatory testing would help, and how the team will account for the finding in your anesthesia plan.
A targeted report is one source of information. Diagnostic evaluation may involve genetic testing or a muscle biopsy contracture test; MHAUS recommends discussing the appropriate test with a genetic counselor. MHAUS: testing for malignant hyperthermia
What the Gene2Rx report assesses
Gene2Rx v4 assesses a defined set of malignant-hyperthermia-associated variants in RYR1 and CACNA1S using eligible original whole-genome sequencing (WGS) data. This assessment is included in the Full Report for WGS customers. Consumer array reports do not include it.
A result with no listed variant detected does not rule out malignant hyperthermia susceptibility. The screen does not identify every possible causal variant, and missing or insufficiently covered sites remain a limitation. A previous uneventful anesthetic also does not establish that a future exposure is safe.
Planning anesthesia
Discuss relevant genetic results, prior reactions, and family history with the anesthesia team. This assessment does not cover every anesthesia risk and should not be used to choose or administer an anesthetic yourself.
Related: succinylcholine and the anesthesia genetics overview.
Can an analgesic use be assumed safe from this genetic result?
No. A targeted screen does not certify the safety of a formulation or exposure. A known personal or family history of malignant hyperthermia should be reviewed with the clinician even if the proposed use is pain relief.
Sources and further reading
Genes that affect Methoxyflurane
See the full list of drugs affected by each gene:
This page explains pharmacogenetic evidence. Clinical decisions depend on your medical history, other medicines, and a qualified clinician's assessment.