Short answer: Premarin and oral estradiol tablets are both estrogen pills for menopause symptoms.12 Premarin is a mix of conjugated estrogens, usually started at 0.3 mg a day. Estradiol tablets come in 0.5 mg, 1 mg and 2 mg, started at 1 to 2 mg a day, given in cycles. Both have very similar approved uses and both carry a boxed warning. Neither label reports a trial against the other.
| Premarin | Estradiol tablets | |
|---|---|---|
| Ingredient | Conjugated estrogens, a mixture of estrogens1 | Estradiol2 |
| Strengths | 0.3 mg to 1.25 mg1 | 0.5 mg, 1 mg and 2 mg2 |
| Start for hot flashes | 0.3 mg daily, adjusted by response1 | 1 to 2 mg daily, adjusted to control symptoms2 |
| Schedule | Daily, or in cycles such as 25 days on and 5 off1 | In cycles, for example 3 weeks on and 1 week off2 |
| Approved for | Hot flashes; vaginal atrophy; low estrogen from hypogonadism, castration or ovarian failure; some breast and prostate cancers (palliation); preventing osteoporosis1 | The same set of uses2 |
| Side effects | Vaginal bleeding 13% on 0.625 mg vs 0% on placebo; breast pain 11% vs 8% (1 year)1 | Headache, breast pain, irregular bleeding, cramps or bloating, nausea; no percentages given2 |
| Missed dose | Take as soon as possible unless the next dose is near (Patient Information)1 | No rule in the label2 |
The estrogen itself. Premarin is a mixture of estrogens called conjugated estrogens.1 Estradiol tablets contain one estrogen, estradiol.2 The milligram numbers are not the same scale, so 1 mg of one is not the same as 1 mg of the other. The estradiol label starts at 1 to 2 mg in cycles; Premarin starts most women at 0.3 mg and can be taken every day or in cycles.21
Both labels have a boxed warning: estrogen alone raises the risk of cancer of the uterus lining in women with a uterus, and the Women's Health Initiative studies found more strokes, blood clots and probable dementia, and with a progestin, breast cancer.12 Women with a uterus also take a progestin under the estradiol label.2 These numbers come from separate trials with different people, lengths and methods, so they are not a head-to-head comparison.
Which estrogen and dose fits is for your prescriber. More detail: Premarin side effects, estradiol tablets side effects, the Premarin and estradiol tablets dosing schedules, the Premarin missed-dose page and the Estradiol (oral tablets) guide.