Have you ruled out any other reason why kitty could be acting like she is in heat? Has she had an ultrasound or xray of her reproductive area to see if the doctor can find a partial ovary? It's possible if it doesn't show on those and the behaviour continues she may need exploratory surgery to find it.
The only thing I found when googling was...
And it certainly does not sound like something I would ever consider using on one of my cats.
Regulation of 'heat' in female cats
Suprelorin (containing Deslorelin 4.7mg) is a slow release gonadotrophin releasing hormone (GnRH) analogue that can suppress fertility in male and female cats by reducing the production of male (testosterone) and female (oestrogen) hormones. The implant works by blocking the pituitary (a gland within the brain) production of GnRH. Thus, the reproductive glands are not primed to produce the hormones responsible for 'heat' in females and sexual activity in males.
Suprelorin is not registered for use in cats,
only dogs, in Australia but the manufacturer has trialled this drug in thousands of cats and it has been shown to be safe in all ages and breeds. Suprelorin has an average duration of action of 8 months but in many cases, will suppress sexual activity for approximately 12 months. Suprelorin uses a polymer base which dissolves over a 12 month period and by the end of this period, cats normally resume sexual activity, with fertility returning to normal at this time.
No side effects have been reported to date using this product and it is superior to using oestrogen/testosterone based drugs for sexual suppression such as Ovarid, which has many reported side effects such as diabetes, pyometron and mammary hypertrophy.