What is agnus castus?
A herb from the chaste tree, also sold as vitex. It has a long history of traditional use around the monthly cycle and is usually taken daily over several months. It interacts with hormonal contraception, so check with a pharmacist first.
How long do these take?
Manufacturers commonly suggest allowing around three months. These are slow, cumulative preparations rather than something you judge in a fortnight.
Can I take them with the pill or HRT?
Check before you do. Several - agnus castus and black cohosh in particular - are known to interact with hormonal medicines. Take the pack to your pharmacist and they can check it against your prescription.
What is the difference between evening primrose and starflower oil?
Both supply gamma-linolenic acid; starflower, also called borage, is the more concentrated source, so the capsules tend to be smaller for the same amount. Beyond that they are used in much the same way.