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Spermicides, contraceptive gels, and Phexxi: how they work, effectiveness, and where to get them

Spermicides, contraceptive gels, and Phexxi: how they work, effectiveness, and where to get them

8 min read

The idea that something could be inserted into the vagina before intercourse to prevent pregnancy isn’t anything new: Written records of the idea date back to 1850 BCE, where documents from Egypt describe vaginally inserting a mix of crocodile dung and fermented dough (really) to prevent pregnancy.

Things have substantially changed over time — and modern-day contraceptive methods involving vaginal insertion look way different than they did almost four thousand years ago. Though the spermicides and contraceptive gels on the market today are not the most effective birth control methods out there, they may be good options for some people — depending on their preferences, medical history, and reproductive goals.

In this post, we’ll highlight the pros and cons of different spermicides and contraceptive gels (and yes, we’ll talk about Phexxi too!). Here are the main takeaways up front:

  • How do spermicides and contraceptive gels work? They work by creating a vaginal environment that's hostile to sperm. These contraceptives reduce the likelihood of conception by blocking sperm from getting to the egg.
  • How effective are spermicides and contraceptive gels? On average, even with "perfect" use (which is virtually impossible), spermicides will only work around 82% of the time. Said another way, if 100 women used spermicides over the course of a year for contraception, 18 of them would get pregnant. Phexxi, when used perfectly, works around 93% of the time but “average” use (86%) would mean 14 out of 100 women would get pregnant. Real-world effectiveness is lower because, as you might've guessed, people don’t always use contraceptives perfectly.
  • What are some pros of spermicides and contraceptive gels? These contraceptives don’t affect your body's hormone production, making them great options for people who prefer hormone-free birth control or for people who cannot take hormonal birth control for medical reasons. Spermicides are also over-the-counter, meaning they don’t require a prescription.
  • Is there anyone spermicides and contraceptive gels may not be right for? People currently using the vaginal ring (for Phexxi in particular), or people who absolutely are not ready to become a parent, should not use spermicides or contraceptive gels. These methods are also not the best matches for people who are prone to recurrent urinary tract infections.

What are spermicides and contraceptive gels?

Spermicides come in many different forms, including:

Phexxi is a vaginal gel that comes in pre-filled applicators; it does not currently come in any other forms.

How do spermicides and contraceptive gels work?

When considering spermicides and contraceptive gels like Phexxi, OB-GYN and Modern Fertility medical advisor Dr. Jane van Dis, MD, FACOG says she "lumps them all together" into one larger category. That's because both spermicides and contraceptive gels work by reducing the likelihood of sperm getting past the cervix and to an egg — unlike some hormonal contraceptives (like birth control pills or the ring), which prevent follicles from developing and ovulation.

How spermicides work

Most spermicides (and many contraceptive gels) contain nonoxynol-9 (N-9 for short), which severely damages or kills sperm by negatively affecting the acrosome — the part of sperm that covers the "head." N-9 is found in a variety of things you may have around your house, like some cleaning and cosmetic products.

How the contraceptive gel Phexxi works

The newest contraceptive gel on the market, Phexxi, works differently, though the underlying logic is the same: damage sperm so they can’t get to the egg, and prevent conception in that way:

  • Phexxi damages sperm by temporarily impacting vaginal pH, modulating it to be in a sperm-unfriendly range. The gel works by keeping vaginal pH in the “normal” range of 4.0-4.5, which is damaging to sperm. Sperm are happiest around a vaginal pH closer to 7 — this is where they are the most viable (AKA have the best chances of survival). The pH of semen, and the pH of the vaginal during sexual arousal, are around this 7ish mark.
  • Phexxi keeps the vaginal pH more acidic with ingredients like lactic acid, citric acid, and potassium bitartrate (fun fact: also known as cream of tartar!). You can think of Phexxi as the opposite of fertility-friendly lube: While fertility-friendly lubes have a pH that is super sperm-friendly, Phexxi intentionally creates a vaginal pH that's detrimental to sperm survival.

How do you use spermicides and contraceptive gels?

Spermicides and contraceptive gels differ in precisely when you need to use them before intercourse:

  • Spermicides need to be put into the vagina between five and 90 minutes before (it’s important to read the labeling of the specific one you get).
  • Phexxi can be used immediately before intercourse, up to an hour before.
  • It’s important to keep in mind that if you use these contraceptives *too* far in advance, they won’t be as effective. Similarly, if you use them after intercourse, they won’t have an effect (which is the case for basically all contraceptives, with the exception of the copper intrauterine device — IUD for short).
  • Spermicides and contraceptive gels can be used concurrently with all other forms of birth control with one exception: It is not recommended that people use Phexxi while also using the vaginal ring.

How effective are spermicides and contraceptive gels at preventing pregnancy?

Let's talk about the effectiveness of these two non-hormonal forms of birth control:

  • Spermicide: If used completely perfectly, about 18 out of every 100 spermicide users will get pregnant per year. But because humans aren’t perfect and spermicides aren’t always used completely perfectly, the real-world stats on this look different: about 28 out of every 100 spermicide users will get pregnant per year, based on average use patterns.
  • Phexxi: Phexxi is comparatively more effective than spermicides at preventing pregnancy. If used completely perfectly, about 7 in every 100 Phexxi users will get pregnant per year. Based on typical use (aka real-world use patterns), 14 out of every 100 Phexxi users will get pregnant per year.
  • How do these rates compare to other types? Some currently available birth control options are remarkably good at preventing pregnancy. For example, the perfect use failure rate for the copper IUD is <1%. Put another way, fewer than 1 out of every 100 copper IUD users will get pregnant per year — which is about on par with things like getting your tubes permanently blocked (aka tubal ligation).

It’s important to assess *your* own ability to use a contraceptive as prescribed when thinking through how effective a contraceptive may be for you personally. Some people may be very confident in their ability to use spermicides and contraceptive gels as prescribed, meaning they should pay more attention to the perfect use success rates. Others may not be as sure they can use a contraceptive perfectly, and may consider weighing typical use (rather than perfect use) success rates more heavily.

How can you get spermicides and contraceptive gels?

Spermicides are over-the-counter, meaning you can buy them without a prescription or recommendation from a healthcare provider. They’re available online, and likely at most stores that sell condoms, lube, and other sexual wellness products. Spermicide might run you between $8 and $15 for a kit.

Phexxi received Food and Drug Administration (FDA) approval as a prescription product, meaning it’s not readily available on pharmacy shelves — and you *do* need a prescription from a healthcare provider to get your hands on it. One box comes with 12 pre-filled applicators, which is something to keep in mind when thinking through how often you’d need to renew your prescription while using Phexxi. The price of Phexxi will depend on where you get it from and whether you have health insurance (and what specific kind).

What are the side effects and risks of spermicides and contraceptive gels?

Just like how hormonal forms of birth control have side effects, so do spermicides and contraceptive gels:

Spermicide reported side effects:

  • Vaginal irritation (burning, itching, rashes)
  • Allergic reaction
  • Irritation or burning while urinating for partners

Phexxi reported side effects:

  • Vaginal burning and itching
  • Vaginal and genital discomfort
  • Pain while urinating
  • Yeast infections
  • Bacterial vaginosis
  • Vaginal discharge
  • Serious side effects may include bladder infection, acute kidney infection, and allergic reactions
  • Sexual partners with penises may also have some discomfort (burning, itching, pain)

The most commonly reported complaint among spermicide users is genital discomfort and irritation (both vaginal and penile). Some people may view this as no biggie, while to others, this may be a really undesirable side effect. Because makers of spermicides don’t need to provide as much documentation as do makers of prescription products, we don’t have great stats on the actual percentage of people experiencing different side effects while using spermicides.

Based on data included in Phexxi’s application for FDA approval, about 18% (almost 1 out of 5) of users reported a vaginal burning sensation, and about 9% (almost 1 out of 10) reported getting a urinary tract infection (UTI). That being said, very few of the people who dropped out of the trial dropped out because of these side effects, meaning they are likely mild or tolerable for most users. Like most other contraceptives other than condoms, Phexxi does not protect against STIs. There’s currently no data on whether it increases your chances of getting HIV or other STIs.

There are two additional considerations that are important to call out for spermicide and contraceptive gels:

  • Because spermicides and contraceptive gels directly impact the vagina, they’re not the best option out there for people who are prone to UTIs or other vaginal infections (and no, if you fall into this category, cranberry juice likely won’t totally save you).
  • They don’t protect against sexually transmitted infections (STIs) like HIV. In fact, it’s likely that frequent spermicide use (like, several times a day frequent) actually *increases* your chances of getting HIV or other STIs from a sexual partner. One good solution here? If you’re going to frequently use spermicides or contraceptive gels, make sure to use condoms to protect against STIs.

According to Dr. van Dis, whatever birth control method you choose, it's "ever more important that both partners participate in pregnancy and STI prevention as access to reproductive healthcare services of all kinds may be sharply limited in the near future."

How do you know if spermicides or contraceptive gels are right for you?

While spermicides and contraceptive gels aren’t the most effective contraceptives we’ve got, that may be right for some people. Some may prefer not to take hormonal birth control or can’t take hormonal birth control because of health reasons, making spermicides and contraceptive gels a good alternative best option. It’s important that people have as wide a range as possible when choosing what contraceptive is right for them, and spermicides and contraceptive gels are key players in the field of non-hormonal contraceptive options.

That being said, if your #1 priority is highly effective pregnancy prevention, spermicide or contraceptive gels on their own aren't ideal. As compared to spermicides alone, success rates are higher when spermicides are used in conjunction with other barrier methods like condoms, sponges, cervical caps, and diaphragms (you’ll need a prescription for these last two), but they’re still not as high as success rates for hormonal contraceptives and the copper IUD.

Your healthcare provider can always walk through the contraceptive options you have based on your preferences and health history. If you want to do your own research or take a deeper dive into these options, the Modern Fertility blog always has your back.

This article was medically reviewed by Dr. Jane van Dis, MD, FACOG. Dr. van Dis is a practicing OB-GYN, Assistant Professor of Obstetrics & Gynecology at the University of Rochester, CEO of Equity Quotient, co-founder of OB Best Practice, and co-founder of TIME'S UP Healthcare.

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Talia Shirazi, PhD

Talia is a clinical product scientist at Modern Fertility. She's passionate about reproductive health + behavioral neuroendocrinology. Talia received her PhD in biological anthropology at Penn State.

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