Veozah and PPIs (Omeprazole, Pantoprazole): What Every Woman Needs to Know

What Is Fezolinetant and Who Is It For?

Fezolinetant (Veozah) is a non-hormonal, oral neurokinin 3 (NK3) receptor antagonist approved by the FDA in May 2023 specifically for moderate-to-severe vasomotor symptoms (VMS) due to menopause. It blocks the NK3 receptor in the hypothalamic thermoregulatory center, directly reducing the frequency and severity of hot flashes without using estrogen or progestin.

Who benefits most

Fezolinetant was studied in perimenopausal and postmenopausal women in the SKYLIGHT 1 and SKYLIGHT 2 trials, where the 45 mg once-daily dose reduced hot flash frequency by approximately 60 percent compared to about 45 percent with placebo at 12 weeks. It is particularly relevant for women who cannot or prefer not to use menopausal hormone therapy, including survivors of hormone-receptor-positive breast cancer, women with a history of venous thromboembolism, and those who simply want a non-hormonal option.

Why drug interactions matter more in this drug class

Fezolinetant is almost entirely metabolized by the cytochrome P450 1A2 (CYP1A2) enzyme in the liver, with minor contributions from CYP2C19 and CYP2C9 according to the Veozah prescribing information. That single-enzyme dependence makes it unusually sensitive to CYP1A2 inhibitors. Inhibit CYP1A2 and fezolinetant plasma concentrations rise, raising the risk of dose-dependent adverse effects, including hepatotoxicity.

How PPIs Work and Why the Drug Class Is Not Uniform

Proton pump inhibitors suppress gastric acid by irreversibly blocking the hydrogen-potassium ATPase pump in parietal cells. They are among the most commonly prescribed medications in the United States, and perimenopausal women take them frequently for gastroesophageal reflux disease (GERD), a condition whose prevalence increases around the menopause transition.

The PPI family is not one drug

Not all PPIs share the same metabolic footprint. Their differences in CYP enzyme activity are the key clinical distinction when combining any PPI with fezolinetant.

| PPI | Primary metabolism | CYP1A2 inhibition strength | |---|---|---| | Omeprazole | CYP2C19, CYP3A4 | Moderate to strong | | Esomeprazole | CYP2C19, CYP3A4 | Moderate | | Pantoprazole | CYP2C19 | Minimal to negligible | | Lansoprazole | CYP2C19, CYP3A4 | Minimal | | Rabeprazole | Non-enzymatic, CYP2C19 | Minimal | | Dexlansoprazole | CYP2C19, CYP3A4 | Minimal |

The critical distinction: omeprazole is a well-documented CYP1A2 inhibitor. A pharmacokinetic study published in Clinical Pharmacology and Therapeutics confirmed that omeprazole raises the area under the curve (AUC) of CYP1A2 substrates meaningfully, a finding replicated across multiple substrates. Pantoprazole has essentially no clinically meaningful CYP1A2 inhibition, which is why prescribers and pharmacists typically recommend it as the preferred PPI in women taking fezolinetant.

The Fezolinetant and Omeprazole Interaction: Mechanism and Magnitude

The interaction is pharmacokinetic, not pharmacodynamic. Omeprazole does not change what fezolinetant does at the NK3 receptor. Instead, it reduces how quickly your liver breaks fezolinetant down.

CYP1A2 inhibition step by step

1. Fezolinetant is absorbed from the gut and reaches the liver via the portal circulation.
2. CYP1A2 enzymes in hepatocytes begin converting fezolinetant to its primary metabolite, ES259564.
3. Omeprazole binds CYP1A2 and partially blocks this conversion.
4. Fezolinetant accumulates in the bloodstream at higher concentrations than the manufacturer modeled for the 45 mg dose.
5. Higher fezolinetant exposure correlates with higher rates of transaminase elevation in dose-finding studies.

What the FDA label says explicitly

The Veozah prescribing information lists "strong or moderate CYP1A2 inhibitors" under contraindications, stating: "Concomitant use with strong or moderate CYP1A2 inhibitors is contraindicated due to increased fezolinetant plasma concentrations and risk of adverse reactions including hepatotoxicity." Omeprazole is classified as a moderate-to-strong CYP1A2 inhibitor at the standard 20 mg and 40 mg doses used clinically.

This is a labeled contraindication. Not a warning. Not a precaution. A contraindication.

The practical framework for clinicians: if a perimenopausal or postmenopausal woman needs both acid suppression and fezolinetant, the choice of PPI matters enormously. Omeprazole should be stopped or switched before fezolinetant is started.

How large is the exposure increase?

The Veozah FDA clinical pharmacology review reports that co-administration with a strong CYP1A2 inhibitor increased fezolinetant AUC by approximately 4.6-fold and maximum concentration (Cmax) by approximately 2.2-fold. Even moderate CYP1A2 inhibitors produced clinically significant increases in exposure. A 4.6-fold AUC increase at the therapeutic dose is not a number that supports a "monitor carefully and continue" approach. It is why the label says contraindicated.

Pantoprazole and Fezolinetant: A Much Safer Pairing

Pantoprazole (Protonix, generic) is the preferred PPI for women taking fezolinetant. Its CYP1A2 inhibition is negligible at therapeutic doses. A dedicated drug interaction study confirmed that pantoprazole does not meaningfully alter the pharmacokinetics of CYP1A2-dependent drugs, making it the practical clinical solution when acid suppression is genuinely needed.

Does pantoprazole affect fezolinetant absorption?

Fezolinetant's solubility is not meaningfully pH-dependent at the studied dose range, so acid suppression itself (raising gastric pH) does not appear to reduce its absorption in any clinically meaningful way based on available data. The interaction concern with omeprazole is purely about CYP1A2 enzyme inhibition, not gastric pH. Switching to pantoprazole removes the enzymatic interaction while preserving adequate acid suppression for most GERD indications.

Other PPI options

Lansoprazole, rabeprazole, and dexlansoprazole are all weak CYP1A2 inhibitors. While no large head-to-head trial has been conducted specifically with fezolinetant against each PPI, the known enzyme profiles suggest these are likely acceptable alternatives. Pantoprazole has the most reassuring profile and the most published supporting data.

Hepatotoxicity Risk: Why This Interaction Is Taken Seriously

Fezolinetant carries an existing hepatotoxicity signal that makes CYP1A2 inhibition particularly dangerous, not just pharmacologically inconvenient.

In the SKYLIGHT 4 long-term safety trial, elevated liver enzymes (alanine aminotransferase or aspartate aminotransferase greater than three times the upper limit of normal) occurred in approximately 2.3 percent of women taking fezolinetant 45 mg daily over 52 weeks, compared to 0.9 percent in the placebo group. Most elevations were asymptomatic and resolved after stopping the drug, but the signal was strong enough for the FDA to require a liver monitoring program.

The Veozah prescribing information requires:

• Liver function tests (ALT, AST, total bilirubin) before starting fezolinetant
• Repeat testing at 3 months
• Repeat testing at 6 months
• Discontinuation if ALT or AST rises to five times the upper limit of normal or if signs of hepatic injury develop

Adding a drug that raises fezolinetant concentrations by approximately 4.6-fold eliminates the safety margin the dose was designed around. The monitoring schedule was built for the 45 mg/day pharmacokinetic profile. Co-administering omeprazole effectively exposes the liver to a pharmacologically higher dose without any corresponding monitoring or dose adjustment data to fall back on.

Other Drug Interactions With Fezolinetant You Should Know About

Omeprazole is the most commonly encountered CYP1A2 inhibitor in perimenopausal women, but it is not the only one. Several other medications in common use during this life stage share the same interaction mechanism.

Drugs to avoid with fezolinetant (CYP1A2 inhibitors)

• Fluvoxamine (a psychiatric medication sometimes used for perimenopausal mood symptoms and hot flashes): strong CYP1A2 inhibitor, contraindicated per the Veozah label
• Ciprofloxacin: moderate CYP1A2 inhibitor, contraindicated
• Enoxacin: strong CYP1A2 inhibitor, contraindicated
• Mexiletine: moderate CYP1A2 inhibitor, contraindicated

Drugs that may reduce fezolinetant levels (CYP1A2 inducers)

Strong CYP1A2 inducers (such as cigarette smoking and certain anticonvulsants) may reduce fezolinetant effectiveness by accelerating its metabolism. The prescribing information advises caution. Perimenopausal women who smoke may see reduced drug efficacy as a result.

CYP1A2 substrates affected by fezolinetant itself

Fezolinetant also weakly inhibits CYP1A2 at therapeutic concentrations, so it may slightly raise levels of other CYP1A2-dependent drugs such as theophylline, clozapine, and certain antidepressants. This is a clinically lower-level concern than the omeprazole interaction, but worth noting with your prescriber.

Life-Stage Considerations: Perimenopause and Postmenopause

Perimenopause

Women in perimenopause are still cycling, at least intermittently, which means estrogen and progesterone fluctuations are ongoing. These hormonal shifts do not directly change CYP1A2 activity in a way that modifies the omeprazole interaction, but they are relevant to the overall clinical picture. GERD tends to worsen in late perimenopause partly because of lower progesterone-mediated relaxation of the lower esophageal sphincter, so PPI use is common precisely when VMS are also peaking. Choosing pantoprazole from the start avoids the interaction problem entirely.

Postmenopause

Postmenopausal women are the primary studied population for fezolinetant. Liver enzyme monitoring is especially relevant in this group because other conditions common in postmenopause, including non-alcoholic fatty liver disease and thyroid dysfunction, can independently raise transaminases. Establishing a clear baseline before starting fezolinetant is more important when there are competing explanations for liver enzyme changes.

PCOS

Women with polycystic ovary syndrome who have been prescribed fezolinetant off-label for hot flashes related to hypothalamic dysfunction should follow the same interaction guidance. The ACOG guidance on PCOS management does not specifically address fezolinetant, but the pharmacokinetic interaction does not differ by diagnosis.

Pregnancy, Lactation, and Contraception

Fezolinetant must not be used during pregnancy.

This section is mandatory and the information is direct. Fezolinetant is not approved for any indication during pregnancy. Animal reproductive studies showed adverse fetal effects, including increased post-implantation loss and reduced fetal weights in rat studies described in the Veozah prescribing information. There are no adequate and well-controlled studies in pregnant humans, nor would such trials be ethically conducted.

Pregnancy category and human data

Fezolinetant does not have a traditional FDA pregnancy letter category (the A/B/C/D/X system was replaced in 2015), but the label carries explicit language stating that the drug "may cause fetal harm." Women of reproductive potential should use effective contraception during treatment.

Perimenopausal women who still have the possibility of pregnancy, even if infrequent, should discuss contraception with their prescriber before starting fezolinetant. The drug is indicated for menopausal VMS, but perimenopause does not mean infertility.

Lactation

No data exist on fezolinetant transfer into human breast milk, its effects on the breastfed infant, or its effects on milk production. The Veozah prescribing information advises that the drug should not be used while breastfeeding. Given the drug's mechanism (NK3 receptor antagonism), which involves neuroendocrine pathways, there is at least theoretical concern about effects on prolactin and milk production, though this has not been studied in humans.

Omeprazole in pregnancy and lactation

For context: omeprazole itself has a long safety record in pregnancy and lactation. A large population-based cohort study published in Gastroenterology found no significant increase in major congenital malformations with first-trimester PPI use. Pantoprazole carries similar reassurance. The pregnancy/lactation concern in this interaction article is specifically about fezolinetant, not about PPIs.

Who This Combination Is Right For and Who Should Avoid It

Appropriate candidates for fezolinetant plus a PPI

• Postmenopausal women with moderate-to-severe VMS who need acid suppression and can switch from omeprazole to pantoprazole
• Women who have been on pantoprazole already and want to add fezolinetant: the interaction risk is low, proceed with standard fezolinetant monitoring
• Women for whom hormone therapy is contraindicated or declined, and who also require long-term acid suppression

Women who should not use this combination as written

• Anyone currently taking omeprazole (or esomeprazole) who cannot switch to an alternative PPI: the combination with fezolinetant is contraindicated, and the prescriber must make a decision about which therapeutic priority takes precedence
• Women taking fluvoxamine or ciprofloxacin concurrently: multiple CYP1A2 inhibitors compound the risk further
• Women with pre-existing elevated liver enzymes: fezolinetant carries independent hepatotoxicity risk; adding a CYP1A2 inhibitor is doubly problematic

What to tell your prescriber

Bring a complete medication list, including over-the-counter PPIs. Omeprazole 20 mg is available without a prescription in the United States, and many women do not think to mention it. The interaction is the same whether omeprazole is prescribed or purchased over the counter.

A useful framing for your conversation: "I take omeprazole for reflux. I know Veozah has a liver monitoring requirement. Is pantoprazole a safe substitute for my reflux so I can start Veozah?"

Evidence Gaps and What Is Extrapolated

Women have historically been underrepresented in drug interaction pharmacokinetic studies, and the fezolinetant-PPI interaction is no exception to that broader pattern. The CYP1A2 inhibition magnitude cited in the Veozah label comes from drug interaction studies, some of which used fluvoxamine or ciprofloxacin as the inhibitor probe, not omeprazole specifically. The classification of omeprazole as a moderate-to-strong CYP1A2 inhibitor is well-established from studies published in the European Journal of Clinical Pharmacology, but a dedicated omeprazole-fezolinetant pharmacokinetic study has not been published in the peer-reviewed literature as of this article's review date.

The contraindication in the Veozah label is based on the known inhibitory potency of omeprazole at CYP1A2 combined with the observed sensitivity of fezolinetant to CYP1A2 inhibition. This is standard regulatory and clinical pharmacology practice. The extrapolation is scientifically sound, but women and their clinicians should understand that the cited AUC increase comes from studies using other probe inhibitors, not omeprazole head-to-head data.

Practical Switching Guide: From Omeprazole to Pantoprazole

Switching PPIs is generally straightforward. Pantoprazole 40 mg once daily in the morning before eating is an approximately equivalent dose to omeprazole 20 mg once daily for most GERD indications, per standard acid-suppression dosing guidance.

Steps to make the switch safely:

1. Confirm with your gastroenterologist or primary care provider that pantoprazole is appropriate for your specific reflux indication. H. Pylori eradication regimens, Barrett's esophagus management, and severe erosive esophagitis may have specific PPI preferences.
2. Switch to pantoprazole at an equivalent dose at least several days before starting fezolinetant. Omeprazole's CYP1A2 inhibitory effect wanes as the drug clears, typically within two to five days of the last dose.
3. Start fezolinetant 45 mg once daily as prescribed once the switch is complete.
4. Get baseline liver function tests before the first fezolinetant dose if you have not already done so.
5. Follow the required monitoring schedule: repeat liver tests at 3 months and 6 months.

If you cannot switch PPIs for any clinical reason, discuss with your prescriber whether fezolinetant is the right choice for your VMS or whether other non-hormonal options (such as low-dose paroxetine 7.5 mg, the only FDA-approved SSRI for VMS, or gabapentin, or lifestyle strategies) might be considered.