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Diazacon ( 20,25 diazacholesterol) is a cholesterol mimic that inhibits cholesterol production and blocks steroid hormone formation. The compound was originally developed by the G.D. Searle Co. for use as a cholesterol-reducing agent in humans. Although the drug was successful in reducing cholesterol levels, its use was discontinued because of side effects.

Diazacon was later studied as a reproductive inhibitor for use in control of pest birds. It was thought that since eggs contain cholesterol, lowering cholesterol might inhibit reproduction. More importantly, 20,25 diazacholesterol may have the ability to block production of hormones necessary for reproduction such as estrogen, progesterone, and testosterone.

Tests showed 20,25 diazacosterol to be effective in reducing reproduction in pigeons, blackbirds, starlings, and sparrows. The product was subsequently registered for pigeon population control under the tradename Ornitrol. In some instances, good results were seen, in others, results were less than optimal. One problem with pigeons is that they breed year round (especially in warm climates). Long-term treatment with high doses of Ornitrol not only became expensive but sometimes muscle tremors developed in the birds.

Diazacon has the same hormone-inhibiting effect in mammals as in birds, and has been shown to limit reproduction in different types of rats. The most promising uses of diazacon would logically be in animals (birds or mammals) that have a limited breeding season. Animals in areas where increased population is a problem could be treated prior to the breeding season without the need to treat throughout the year.

Avian Infertility

To date, diazacon has been studied in Japanese quail, ring-necked doves, and brown-headed cowbirds. Studies have shown significant differences in absorption and effectiveness of diazacon among bird species studied. In Japanese quail, diazacon effectively lowered cholesterol and reproductive hormone production in both sexes for several months following treatment. In female Japanese quail, egg-laying, fertility, and hatchability of eggs decreased significantly after one week of treatment and remained significantly reduced for several months. In ring-necked doves, cholesterol levels were significantly reduced for several months after treatment. Studies in brown-headed cowbirds showed a significant reduction in cholesterol, although subsequent studies are needed to determine the optimal dose and how long the effect lasts. Currently, diazacon absorption and effectiveness are being studied in American crows and in waterfowl.

A Preliminary Field Trial of Diazacon Use in Prairie Dogs

A small study was undertaken to test whether diazacon would be effective in prairie dogs. Due to delays in obtaining the proper permits, treatment began later than planned. Even so, the average number of young as a proportion of adults at treated sites compared to control sites was reduced by about 59%. These results suggest that , at least in animals with a single breeding season, diazacon has potential for use as a fertility control agent.

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GnRH Immunocontraception (Technical Discussion)
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