The thirty one painted oak wooden boxes from the beginning of the 17th century, the legacy of Master Maré, apothecary to the Hospice Saint Roch in Issoudun in 1646, are amongst the oldest of their kind in France. They feature a rich ornamental decoration of flowers, animals or human figures. A Latin inscription in the upper cartouche identifies the remedy contained within. The use of wooden boxes, in chestnut or oak, sometimes cylinder shaped, was advocated from the Middle Ages to keep hydrophilic drugs, dried plants, roots and barks, gums, resins, horns, nails, bones and ivories.
Pyrethrum was used in poultices for headaches.
I have no idea why it is represented by a boar-cum-fish.
Rabelais described them from 1534 in the prologue of Gargantua: [My translation] Silènes* were small boxes which you used to see in apothecary shops, painted on the outside with joyous and frivolous figures, like harpies, satyrs, bridled goslings, horned hares, basted ducks, flying bucks, lemon tree antlered stags, and other such painted enjoyable counterfeits to make everyone laugh...but inside them they store fine drugs like balm, ambergris, cardamom, musk, civet, jewels and other precious things.'
Labdanum is a resin from rockroses Cistus spp, gathered in medieval times
by combing it from the hair of the goats that grazed on the shrubs.
There is no connection to unicorns so far as I know.
The painted representations of strange animals, associated with products from Asia or the Americas are borrowed directly from scientific works of the 16th century, such as 'Monsters and Prodigies' by Ambroise Paré, published in 1585 or the 'Universal Cosmography' by André Thevet, from 1575.
Opium has been used as a painkiller since Neolithic times. I'm interested
that the image on the box is not of bog standard single lilac coloured flowers, but of a fancy (quite common) mutation which produces flowers like a pompom.