Vienva 28 Day Drug Interactions: What to Avoid and What to Tell Your Doctor

Vienva 28 Day can interact with a number of medications, supplements, and foods. Some interactions reduce Vienva's effectiveness — increasing your risk of unintended pregnancy. Others can cause serious side effects or make other medications less effective. Here's what every Vienva user should know before starting or changing any medication.

The Critical Interaction: Viekira Pak (CONTRAINDICATED)

The most serious drug interaction with Vienva is with Viekira Pak — an HCV (hepatitis C) treatment containing ombitasvir/paritaprevir/ritonavir (with or without dasabuvir). This combination is CONTRAINDICATED with Vienva 28 Day.

Taking Vienva with Viekira Pak can cause a significant increase in liver enzyme (ALT) levels, potentially causing liver injury. If you need HCV treatment with this drug combination, you must stop Vienva before starting and switch to a non-estrogen-containing contraceptive during HCV treatment. You can restart Vienva approximately 2 weeks after completing Viekira Pak treatment.

Drugs That Make Vienva Less Effective (Reduced Effectiveness Interactions)

These medications speed up how quickly your body metabolizes Vienva's hormones, reducing hormone levels in your bloodstream below the effective contraceptive threshold. If you take any of these, discuss backup contraception with your provider:

Rifampin (Rifadin): An antibiotic used for tuberculosis. Among the strongest inducers of Vienva metabolism. Can render Vienva ineffective. Use backup contraception for at least 28 days after stopping rifampin.

Carbamazepine (Tegretol): Anti-seizure medication. Strongly reduces Vienva efficacy. Discuss a more reliable contraceptive option (like an IUD) with your neurologist and gynecologist.

Phenytoin (Dilantin): Another anti-epileptic drug. Significantly reduces levonorgestrel and ethinyl estradiol plasma levels.

Phenobarbital and other barbiturates: Common anti-seizure medications that can reduce contraceptive hormone levels.

Topiramate (Topamax): Used for epilepsy and migraines. Can reduce Vienva's efficacy, particularly at doses above 200 mg/day.

Oxcarbazepine (Trileptal): Related to carbamazepine; also a significant inducer of oral contraceptive metabolism.

Modafinil (Provigil): A wakefulness drug used for narcolepsy or shift work sleep disorder. May reduce the efficacy of hormonal contraceptives.

Ritonavir and other HIV protease inhibitors: Can have complex and variable interactions with oral contraceptive hormones — some reduce efficacy, some increase hormone levels. Always check with your HIV specialist and OB/GYN.

Herbal Supplements That Can Reduce Effectiveness

St. John's Wort (Hypericum perforatum): A widely available herbal supplement for depression. St. John's Wort induces CYP450 enzymes, increasing the breakdown of both levonorgestrel and ethinyl estradiol. This can reduce blood levels significantly and has been associated with breakthrough pregnancies. Avoid while taking Vienva.

Food Interactions: Grapefruit

Grapefruit and grapefruit juice inhibit CYP3A4 enzymes, which can increase ethinyl estradiol levels in the blood. This doesn't reduce contraceptive efficacy, but it can increase the risk of estrogen-related side effects (nausea, breast tenderness, headaches). Talk to your provider if you regularly consume grapefruit.

Antibiotics and Vienva: What's the Real Story?

For decades, patients were told that all antibiotics reduce birth control effectiveness. Current evidence shows that most common antibiotics (amoxicillin, azithromycin, cephalosporins, doxycycline) do NOT significantly reduce Vienva's efficacy. The one clear exception is rifampin (rifampicin), which is a powerful enzyme inducer.

However, if antibiotics cause significant vomiting or diarrhea, absorption of Vienva may be reduced. Use backup contraception if you experience vomiting within 3-4 hours of taking a pill.

Drugs Whose Effects Are Changed by Vienva

Vienva can also affect how other drugs work in your body:

Warfarin: Estrogen-containing pills can affect INR levels in patients on warfarin. Monitor INR more closely when starting or stopping Vienva.

Cyclosporine: Ethinyl estradiol may increase cyclosporine plasma levels. Monitor closely.

Thyroid hormone replacements: Estrogen increases thyroid-binding globulin, which may increase the dosing requirement for thyroid hormone in patients on levothyroxine.

What to Tell Your Doctor

Before starting Vienva 28 Day, provide your prescriber with a complete list of all prescription medications, OTC drugs, vitamins, minerals, and herbal supplements you use. This is especially important if you are being treated for epilepsy, HIV, hepatitis C, tuberculosis, or depression. See our companion guide on Vienva 28 Day side effects for more on safety. To find Vienva in stock near you, visit medfinder.