Tri-Lo-Estarylla is a prescription birth control pill that contains two hormones, a progestin (norgestimate) and an estrogen (ethinyl estradiol), in a triphasic formulation. It’s a generic equivalent of Ortho Tri-Cyclen Lo, meaning it contains the same active ingredients at the same doses but typically costs less. Each pack contains 28 tablets: 21 active hormone pills and 7 inactive pills you take during your period week.
How the Triphasic Design Works
Unlike monophasic pills that deliver the same hormone dose every day, Tri-Lo-Estarylla changes the amount of progestin across three phases while keeping estrogen constant. The pack is color-coded to match each phase:
- Days 1 to 7 (white tablets): 0.18 mg norgestimate + 0.025 mg ethinyl estradiol
- Days 8 to 14 (light blue tablets): 0.215 mg norgestimate + 0.025 mg ethinyl estradiol
- Days 15 to 21 (blue tablets): 0.25 mg norgestimate + 0.025 mg ethinyl estradiol
- Days 22 to 28 (green tablets): No hormones (inactive pills)
The progestin gradually increases over the three weeks, while the estrogen stays at a low dose of 0.025 mg throughout. This stepping pattern was originally designed to reduce side effects compared to fixed-dose pills and to more closely mimic your body’s natural hormone fluctuations during a menstrual cycle. The “Lo” in the name refers to the low estrogen dose, which is lower than what you’d find in standard-dose combination pills.
Because the pills aren’t interchangeable, taking them in the correct order matters. If you mix up the sequence, you could get a lower hormone dose than intended during a given week, which may reduce effectiveness or cause breakthrough bleeding.
How It Prevents Pregnancy
Tri-Lo-Estarylla works through three mechanisms. The primary one is suppressing ovulation, so your ovaries don’t release an egg each month. It also thickens cervical mucus, making it harder for sperm to reach an egg, and thins the uterine lining, making implantation less likely. With typical use (accounting for missed pills and human error), combination birth control pills are about 91% effective. With perfect use, that number rises to over 99%.
Common Side Effects
Most side effects are mild and often improve within the first two to three months as your body adjusts. The most frequently reported ones include headaches (including migraines), nausea and vomiting, breast tenderness or swelling, stomach pain, painful periods, mood changes including depression, acne, vaginal infections, bloating, weight gain, and fatigue.
Nausea tends to be the most common early complaint and often resolves if you take the pill with food or at bedtime. Breakthrough bleeding or spotting between periods is also typical in the first few cycles, particularly with triphasic pills where hormone levels shift weekly.
Serious Risks
Like all combination birth control pills, Tri-Lo-Estarylla carries a small but real risk of blood clots, stroke, and heart attack. This risk increases significantly if you smoke and are over 35. People in that category should not use combination oral contraceptives. Other factors that raise cardiovascular risk include a history of blood clots, high blood pressure, certain inherited clotting disorders, and prolonged immobility (such as after surgery or during long flights).
Medications That Reduce Effectiveness
Certain drugs speed up how your liver breaks down the hormones in Tri-Lo-Estarylla, which can lower the pill’s effectiveness or cause breakthrough bleeding. The most notable ones include some anti-seizure medications (phenytoin, carbamazepine, topiramate, oxcarbazepine, felbamate, rufinamide), the antibiotic rifampin and related drugs, the antifungal griseofulvin, and St. John’s wort, an herbal supplement commonly used for depression. If you take any of these, you may need backup contraception or an alternative birth control method.
How It Compares to Similar Pills
Tri-Lo-Estarylla belongs to a large family of norgestimate/ethinyl estradiol combination pills. The name can be confusing because there are many closely related products. Estarylla is the monophasic version (same hormones every day, higher estrogen dose). Tri-Estarylla is the triphasic version with a standard estrogen dose. Tri-Lo-Estarylla is the triphasic version with a low estrogen dose, making it the generic match for Ortho Tri-Cyclen Lo specifically.
Other generics with the same formulation include Tri-Lo-Sprintec, Tri-Lo-Mili, Tri-Lo-Marzia, and Tri-Lo-Linyah. These are all therapeutically equivalent, meaning they contain the same active ingredients at the same doses. Differences between them come down to inactive ingredients, tablet coatings, and price. If one generic causes issues like an allergic reaction to a dye or filler, switching to another version of the same formulation is a reasonable option.
Taking the Pills Correctly
You take one pill at the same time every day for 28 days. The first 21 are hormone pills taken in order (white, then light blue, then blue). The last 7 green tablets are placebo pills with no active ingredients. Your period typically starts during this placebo week. After finishing all 28 tablets, you start a new pack the next day with no gap.
If you miss one active pill, take it as soon as you remember, even if that means taking two pills in one day. If you miss two or more active pills, the instructions depend on which week of the pack you’re in, but using backup contraception (like condoms) for at least seven days is a standard precaution. Missing inactive green pills doesn’t affect your protection since those contain no hormones.
One detail worth noting: the inactive tablets in Tri-Lo-Estarylla contain soy-derived lecithin and lactose. If you have a severe soy allergy or significant lactose sensitivity, mention this to your prescriber, though the amounts are very small.