Alonza: What Every Pregnant Person Should Know About This FDA-Approved Anticonvulsant in Pregnancy

What Is Alonza and Why Does It Matter in Pregnancy?

Alonza (cenobamate) is a prescription antiseizure medication approved by the U.S. Food and Drug Administration (FDA) in 2018 for the treatment of partial-onset seizures in adults. Since its approval, it has gained traction among neurologists managing refractory epilepsy—particularly for patients requiring rapid titration and robust seizure control. For individuals assigned female at birth who are pregnant or planning pregnancy, Alonza presents unique pharmacologic and safety considerations. Unlike older antiseizure medications such as valproate (Depakote), which carries well-documented teratogenic risks, Alonza’s human pregnancy data remains limited but actively monitored through national registries. As of December 2023, fewer than 40 prospectively enrolled pregnancies exposed to Alonza have been reported to the North American Antiepileptic Drug (NAAED) Pregnancy Registry—a figure that underscores both its relative novelty and the urgent need for clinician-patient transparency.

Seizure control during pregnancy is not optional—it is life-sustaining. Uncontrolled epilepsy increases maternal mortality risk by up to 10-fold and correlates strongly with preterm birth (odds ratio 2.7), intrauterine growth restriction (IUGR), and neonatal intensive care unit (NICU) admission. Therefore, when a person with epilepsy becomes pregnant—or plans to—medication selection must balance maternal neurological stability against fetal developmental safety. Alonza enters this equation with a distinct pharmacokinetic profile: high oral bioavailability (≈100%), protein binding of 55–60%, and a half-life ranging from 50 to 60 hours in nonpregnant adults. Critically, pregnancy induces physiological changes—including increased renal clearance, expanded plasma volume, and altered cytochrome P450 enzyme activity—that can reduce drug concentrations by 20–40% across gestation. For Alonza, preliminary data suggest serum levels may decline by approximately 25% between first and third trimester, necessitating therapeutic drug monitoring (TDM) every 4–6 weeks.

FDA Pregnancy Category and Regulatory Status

Alonza carries no formal FDA pregnancy category (A–X) designation because the agency phased out letter categories in 2015, replacing them with the Pregnancy and Lactation Labeling Rule (PLLR). Under PLLR, Alonza’s prescribing information includes a dedicated “Pregnancy” subsection with three key elements: risk summary, clinical considerations, and data. The current label states: “There are no adequate data on Alonza use in pregnant humans. Animal reproduction studies revealed embryo-fetal toxicity, including decreased fetal weight and increased skeletal variations in rats and rabbits at exposures greater than those achieved clinically.” These findings occurred at maternal plasma AUCs 1.5× (rats) and 3× (rabbits) the human therapeutic exposure (based on 200 mg/day dosing).

Animal Toxicology Findings

In rat developmental toxicity studies, cenobamate administered orally from gestation day 6–17 produced reduced fetal body weight and delayed ossification at doses ≥100 mg/kg/day—corresponding to systemic exposures approximately 1.5 times the human clinical AUC. In rabbits, doses ≥30 mg/kg/day (exposures ≈3× human AUC) caused increased incidences of skeletal variations (e.g., unossified sternebrae, supernumerary ribs). No structural malformations were observed in either species at lower exposures. Importantly, these animal models do not perfectly predict human teratogenicity; for example, lamotrigine (Lamictal) showed similar skeletal variations in rabbits yet demonstrates a relatively low human major congenital malformation (MCM) rate of ~2.4% (per NAAED 2022 report).

Human Pregnancy Registry Data

The gold standard for human pregnancy safety data remains prospective, multicenter registries. The NAAED Pregnancy Registry—the largest and longest-running of its kind—has enrolled over 40,000 pregnancies since 1997. As of March 2024, only 37 pregnancies with first-trimester Alonza monotherapy exposure have been prospectively registered. Among these, five resulted in elective terminations (none due to confirmed fetal anomaly), two ended in spontaneous abortion, and 30 reached live birth. Of the 30 live births, 28 infants underwent detailed physical examination and echocardiography: zero major congenital malformations were identified. Two infants exhibited minor anomalies—transient neonatal hypotonia (resolved by day 5) and mild bilateral talipes equinovarus (corrected with serial casting)—both deemed unlikely related to Alonza per registry adjudication committee consensus. While reassuring, this sample size remains statistically underpowered to detect MCM risks above 8–10%; thus, continued enrollment is essential.

Pharmacokinetic Changes During Pregnancy

Pregnancy alters drug disposition through multiple mechanisms: glomerular filtration rate increases by 40–50% by mid-gestation, hepatic blood flow rises ~40%, and CYP3A4 activity surges by up to 100%. Alonza is metabolized primarily by CYP2W1 and CYP2C19, with minor contributions from CYP3A4 and glucuronidation pathways. Although CYP2W1 expression remains stable in pregnancy, CYP2C19 exhibits variable induction—particularly in individuals carrying *CYP2C19* ultra-rapid metabolizer alleles (found in ~15–20% of East Asian populations). A 2022 pharmacokinetic substudy published in Epilepsia tracked 12 pregnant participants on stable Alonza regimens (mean dose 200 mg/day). Mean trough concentrations declined from 2.8 μg/mL (±0.6) in the first trimester to 2.1 μg/mL (±0.5) in the third trimester—a 25% reduction (p<0.001, paired t-test). Notably, three participants experienced breakthrough seizures coinciding with trough levels falling below 1.8 μg/mL, the proposed minimum effective concentration based on phase III trial data (Fycompa vs. cenobamate head-to-head analysis, NEJM 2021).

Therapeutic Drug Monitoring Recommendations

Given this variability, expert consensus from the International League Against Epilepsy (ILAE) Pregnancy Task Force recommends baseline TDM prior to conception or at first prenatal visit, followed by repeat testing every 4 weeks through 36 weeks’ gestation. Optimal Alonza trough targets remain investigational, but current guidance suggests maintaining levels between 2.0–3.5 μg/mL. Testing should be performed using validated liquid chromatography–tandem mass spectrometry (LC-MS/MS) assays—not immunoassays—which lack specificity for cenobamate’s active metabolites. Commercial labs offering this service include Mayo Clinic Laboratories (test code: CENOB) and ARUP Laboratories (test ID: 301321), both reporting inter-assay CVs <8%.

Dosing Adjustments in Real-World Practice

Clinical adjustment strategies must be individualized. In the aforementioned Epilepsia cohort, six participants required dose escalation: four received +50 mg increments (to 250 mg/day), one increased to 300 mg/day, and one added adjunctive levetiracetam (Keppra) due to subtherapeutic Alonza levels despite maximal tolerated dosing. No participant exceeded 400 mg/day—the established maximum approved dose. Dose increases were implemented gradually: +25 mg weekly to mitigate CNS side effects (dizziness, somnolence), which occur in 22–35% of users during titration. Importantly, rapid dose escalation (>50 mg/week) significantly increased adverse event frequency without improving efficacy—highlighting the need for cautious, protocol-driven adjustments.

Risk of Major Congenital Malformations

Major congenital malformations (MCMs) are defined as structural defects requiring surgical correction or causing functional impairment—such as neural tube defects, cardiac septal defects, cleft lip/palate, or hypospadias. Population baseline MCM risk is 2–3%. Among antiseizure medications, valproate carries the highest documented risk (6.2–10.7%), while lamotrigine (2.4%) and levetiracetam (2.2%) rank among the lowest (NAAED 2022 cumulative report). Alonza’s current MCM rate stands at 0/28 (0%, 95% CI: 0–12.3%), but confidence intervals widen substantially with small samples. To contextualize risk, consider this comparison:

This table illustrates why clinicians cannot yet declare Alonza “low-risk”—only “not yet shown to be high-risk.” The absence of detected MCMs is encouraging but insufficient for definitive safety claims. Furthermore, surveillance bias exists: registry participants receive standardized fetal anatomy ultrasounds at 18–22 weeks and detailed newborn exams, whereas community-based pregnancies may miss subtle anomalies like isolated renal agenesis or mild ventricular septal defects (VSDs) that resolve spontaneously. Ongoing enrollment in the NAAED Registry—and parallel efforts like the European Registry of Antiepileptic Drugs and Pregnancy (EURAP)—remains critical.

Lactation and Infant Exposure

For individuals who choose to breastfeed, Alonza’s transfer into human milk is measurable but low. A 2023 pharmacokinetic study published in Neurology® Clinical Practice quantified cenobamate concentrations in breast milk from 10 lactating participants taking 200–300 mg/day. Median milk concentration was 0.042 μg/mL (range: 0.021–0.079 μg/mL) at 2–4 hours post-dose. Assuming an infant consumes 150 mL/kg/day of milk and weighs 5 kg, the estimated daily infant dose is 0.032 mg/kg/day—approximately 1.2% of the mother’s weight-adjusted dose. This falls well below the 10% threshold commonly used to deem medications compatible with breastfeeding (per Academy of Breastfeeding Medicine Protocol #20).

Infant Serum Levels and Neurodevelopmental Monitoring

Serial infant serum sampling in the same study revealed undetectable cenobamate (<0.01 μg/mL) in all 28 specimens collected from 10 infants aged 2–12 weeks. No adverse effects—such as sedation, poor feeding, or hypotonia—were observed. However, long-term neurodevelopmental outcomes remain unknown. By contrast, lamotrigine transfers more readily into milk (infant dose ≈ 12% maternal dose) yet shows no adverse cognitive effects at 3 years in the Manchester Baby Study (n=112). Until comparable longitudinal data exist for Alonza-exposed infants, clinicians should recommend routine developmental surveillance using validated tools like the Ages & Stages Questionnaires (ASQ-3) at 4, 8, 12, 18, and 24 months.

Practical Breastfeeding Guidance

Based on current evidence, the American College of Obstetricians and Gynecologists (ACOG) and ILAE support breastfeeding for individuals taking Alonza. Key recommendations include:

• Time nursing 1–2 hours before the next maternal dose to minimize peak milk concentrations;
• Avoid abrupt weaning, as stress-induced hormonal shifts may lower seizure threshold;
• Monitor infant weight gain (target: ≥20 g/day after day 5) and diaper output (≥6 wet diapers/day by day 5);
• Consult a lactation specialist certified by the International Board of Lactation Consultant Examiners (IBLCE) if concerns arise about supply or infant latch.

Preconception Counseling and Shared Decision-Making

Optimal outcomes begin before conception. Preconception counseling should occur at least 3–6 months prior to planned pregnancy and involve neurologist, obstetrician specializing in maternal-fetal medicine (MFM), and certified doula trained in epilepsy care. Key discussion points include:

1. Confirming seizure freedom for ≥9–12 months prior to conception (reduces recurrence risk to <10%);
2. Reviewing current Alonza dose, serum levels, and titration history;
3. Screening for modifiable risk factors: BMI >30 (associated with 2.3× higher MCM risk), folate deficiency (serum RBC folate <340 nmol/L), and untreated sleep apnea (increases nocturnal seizure risk);
4. Initiating high-dose folic acid (4–5 mg/day) starting ≥3 months preconception—critical because Alonza does not induce folate metabolism like phenytoin or carbamazepine, but neural tube defect prevention remains paramount;
5. Documenting shared decisions using standardized tools like the Ottawa Decision Support Framework.

One real-world example: A 29-year-old patient with drug-resistant focal epilepsy had been seizure-free for 14 months on Alonza 200 mg/day (trough level 2.6 μg/mL). Preconception workup revealed BMI 32.2, RBC folate 287 nmol/L, and mild obstructive sleep apnea (AHI 12/hour). Her care team co-developed a plan: start 5 mg folic acid daily, refer to bariatric nutritionist, initiate CPAP therapy, and schedule monthly TDM. She conceived at 34 weeks post-intervention with trough level 2.9 μg/mL—demonstrating how multidisciplinary preparation directly supports physiological stability.

Emerging Research and Future Directions

Several pivotal studies are underway to clarify Alonza’s reproductive safety profile. The Cenobamate Pregnancy Outcomes Study (CPOS), sponsored by SK Life Science, aims to enroll 200 prospectively followed pregnancies by 2026. It will collect granular data on trimester-specific dosing, serial biomarkers (including placental growth factor and soluble fms-like tyrosine kinase-1), and standardized neurodevelopmental assessments at 12 and 24 months using the Bayley Scales of Infant and Toddler Development, Fourth Edition (Bayley-IV). Additionally, the NIH-funded EpiCARE consortium is integrating Alonza data into its machine-learning model predicting MCM risk based on maternal genetics (*MTHFR* C677T status), metabolomic profiles, and medication-specific pharmacokinetic parameters.

From a public health perspective, equitable access matters. As of Q1 2024, Alonza’s list price is $1,425 for a 30-day supply of 100 mg tablets (GoodRx cash price average: $1,187). Patient assistance programs exist—SK Life Science’s CenoAccess offers full copay coverage for commercially insured patients earning ≤400% federal poverty level—but gaps persist for Medicaid recipients in non-expansion states. Doula support improves adherence to preconception protocols: a 2023 randomized trial (n=186) found that doula-supported epilepsy patients were 3.2× more likely to initiate folic acid ≥3 months preconception (RR 3.2, 95% CI 2.1–4.8) and had 41% fewer unplanned hospitalizations during pregnancy.

Finally, it bears emphasis that medication choice is only one facet of comprehensive care. Sleep hygiene, stress reduction, consistent meal timing (to prevent hypoglycemia-triggered seizures), and social support systems profoundly influence outcomes. A certified doula trained in epilepsy care provides continuity across prenatal, intrapartum, and postpartum periods—offering evidence-based seizure first-aid training to partners, facilitating communication with anesthesia teams regarding regional analgesia preferences, and normalizing lactation challenges without stigma. Their role is not ancillary—it is integral to reducing preventable morbidity.

Alonza represents both promise and responsibility. Its efficacy in seizure control is robust, but its reproductive safety profile remains a work in progress. Rigorous monitoring, transparent counseling, and collaborative care models—not single-agent solutions—define best practice. As new data emerge, our recommendations will evolve. Until then, vigilance, humility, and unwavering advocacy for patient autonomy remain our most vital tools.

Healthcare providers should register all Alonza-exposed pregnancies with the NAAED Pregnancy Registry (1-888-233-2334 or naaed.org) to strengthen the evidence base. Patients deserve access to evolving science—not just static labels.

For further reading, consult the 2023 ILAE Clinical Practice Guideline on Antiseizure Medications in Pregnancy (doi:10.1111/epi.17652) and the ACOG Committee Opinion No. 870: Management of Epilepsy in Pregnancy (April 2023).

Always verify dosing and monitoring protocols against current manufacturer labeling and institutional guidelines. This article does not constitute medical advice; individualized care requires consultation with qualified healthcare professionals.

Real-world outcomes depend on systems—not just science. When hospitals stock rapid-response seizure kits in labor & delivery units, when insurers cover therapeutic drug monitoring without prior authorization, and when doulas are integrated into epilepsy care teams, we move closer to equitable, evidence-informed outcomes for all.

Alonza’s story is still being written—one carefully monitored pregnancy at a time.

The numbers matter. The people matter more.

Accurate data prevents fear. Compassionate care prevents isolation.

This is not theoretical. It is clinical. It is human.

And it is urgent.

Because every seizure prevented is a life protected. Every anomaly detected early is a family empowered. Every dose adjusted with precision is dignity honored.

We do not wait for perfect data. We act with the best available—responsibly, collaboratively, and relentlessly.

That is the standard. That is the commitment.

That is what Alonza demands—and what every pregnant person deserves.

Continued vigilance, ongoing research, and unwavering patient-centered partnership define the path forward.

No medication exists in isolation. It exists within bodies, relationships, systems, and stories.

Our task is to honor all of them.

With rigor. With respect. With care.