Anastrozole and Cabergoline are each a small molecule rather than a peptide.
Same target, different schedules: Anastrozole daily; Cabergoline twice a week.
| Comparison | Anastrozole Arimidex · ANA | Cabergoline Dostinex · Caber |
|---|---|---|
| How it works | How it works Anastrozole works upstream of the receptor, on supply rather than on signal. | How it works Prolactin is held down by dopamine. Cabergoline supplies a long-lasting dopamine signal. |
| What it is | An aromatase inhibitor approved for postmenopausal breast cancer. | A prolactin drug whose label asks for an echocardiogram before the first dose. |
| Status | FDA approvedFDA-approved | FDA approvedFDA-approved |
| Typical dose | 1 mg per day | 0.25–1 mg per week |
| How often | Daily | Twice a week |
| Stays active | About 47 hours | About 63 to 69 hours |
| Dose comes from | FDA drug label | FDA drug label |
| Cycled? | Continuous, for years in the trials FDA drug label | Continuous, with the dose reassessed rather than paused FDA drug label |
| What it does | ||
| Drug class | Aromatase inhibitor (oral, not a peptide) | Ergot dopamine agonist (oral, not a peptide) |
| Used for | A breast cancer drug used on the research market to hold estrogen down during a testosterone or anabolic cycle. | A prescription drug that lowers prolactin. On the research market it is used during a cycle, and for its effect on libido. |
| Receptors hit | — | — |
| Numbers | ||
| Full dose line | 1 mg per day | 0.25 up to 1 mg twice a week |
| Why that cycle | Given daily and without a break for the duration of treatment. The intermittent twice-weekly dosing used alongside testosterone is a community pattern built around symptom control rather than anything from a trial. | The label says to use the lowest effective dose and to reassess periodically whether treatment should continue, and to check prolactin after stopping to see whether it needs restarting. That is dose management rather than cycling. The valve monitoring interval of 6 to 12 months applies for as long as it is taken. |
| Weight / effect | Not measured in a trial | Not measured in a trial |
| Chain length | Not disclosed | Not disclosed |
| Common vial | — | — |
| Before you start | ||
| Route | By mouth (oral) | By mouth (oral) |
| Do not use if | Pregnancy Existing osteoporosis or low bone density, without a plan to manage it Known hypersensitivity to anastrozole Pre-existing ischaemic heart disease, where the label notes more ischaemic events on anastrozole than on tamoxifen Banned in drug-tested sport | Any existing heart valve disease, including valve leaflet thickening seen on an echocardiogram A history of pericardial, pleural, pulmonary or retroperitoneal fibrosis Uncontrolled high blood pressure Known hypersensitivity to ergot derivatives Suppressing milk production after birth, which the label advises against |
What people actually report
Anastrozole
- It lowers bone mineral density, and the effect showed up within twelve months in the trials.
- Cholesterol rises. In the ATAC trial 9 percent of women on anastrozole had raised cholesterol against 3.5 percent on tamoxifen.
- Joint pain and stiffness are the complaints that most often stop people taking it.
- Banned in drug-tested sport at all times.
Stop and get help if
- Chest pain, or new breathlessness on exertion
- A bone fracture from a minor fall or knock
Cabergoline
- The label asks for an echocardiogram before the first dose, and every 6 to 12 months after it, to look for heart valve damage.
- Existing valve disease is a contraindication, not a caution.
- It is an ergot derivative, and fibrosis of the heart, lungs, chest lining and abdomen have all been reported.
- Compulsive behaviour including gambling and hypersexuality is a documented class effect of dopamine agonists.
Stop and get help if
- Shortness of breath, difficulty breathing when lying flat, or swelling in the legs
- Chest pain, or a persistent cough
Side effects are what users and trials report most often, not a complete list. Anything sudden, spreading, or breathing-related is an emergency regardless of which compound caused it.
People also compare
This comparison does not cover cost, long-term safety, or how you personally will respond. Effect figures come from separate trials in different populations and are not always directly comparable to each other. Nothing here is medical advice or a recommendation to use any of these. Talk to a clinician about your own situation.