Hydroxydione

The first steroid intravenous anesthetic (1955); a water-soluble GABA-A positive modulator whose slow onset and thrombophlebitis retired it but which founded the neurosteroid anesthetic lineage that runs to alfaxalone and brexanolone.

In the anesthetic practice of its time hydroxydione was regarded as having an unusually wide therapeutic margin, with the original animal pharmacology emphasizing low acute toxicity and comparatively little of the myocardial and respiratory depression seen with contemporaneous barbiturates. It produced no analgesia, so it was combined with other agents for surgery, and it lacked meaningful glucocorticoid or progestational activity at hypnotic doses, although several mid-century studies examined its effects on adrenal function and acid-base balance.

The defining safety problem was local rather than systemic: the injected solution caused a high incidence of pain, venous irritation, thrombophlebitis, and deep vein thrombosis, attributed to the physicochemical properties of the succinate vehicle and its effect on the vein wall, and reformulation with glycine buffering only partially mitigated this. The slow, cumulative onset also created a practical hazard of overdosing by premature repeat injection. These issues, not systemic organ toxicity, are why the drug was withdrawn. Hydroxydione is of historical and pharmacological interest only and has no current medical or supplemental use.

Interest in steroid anesthesia originated with Hans Selye, who reported in 1941 that certain endogenous steroids such as progesterone and deoxycorticosterone could induce rapid, reversible anesthesia in rodents, an effect too fast to be hormonal. Chemists at Pfizer, led by S. Y. P'an and G. D. Laubach, pursued a steroid that retained this anesthetic action while being safe and, critically, water-soluble enough to inject.

Their solution was 21-hydroxypregnane-3,20-dione esterified at the 21 position with succinic acid, and the foundational 1955 report in the Journal of Pharmacology and Experimental Therapeutics described the general anesthetic and pharmacological properties of this soluble steroid. The compound reached clinical use almost immediately as Viadril in the United States and as Presuren in continental Europe, and confirmatory pharmacology and the first human anesthetic series appeared in 1956 and 1957.

Through the late 1950s and 1960s it was used widely, including in obstetric analgesia, ophthalmic surgery, pediatric cases, and neurosurgery, and reformulations such as Viadril G, which buffered the preparation with glycine, were introduced specifically to reduce venous irritation. Two problems proved decisive: onset was slow, often several minutes, making titration awkward, and injection frequently caused thrombophlebitis and venous thrombosis.

These liabilities, together with the arrival of more tractable agents, drove hydroxydione from practice by the 1970s. Its scientific legacy is large, for it proved that a purpose-built steroid could serve as a controllable general anesthetic and directly seeded the development of alphaxalone-alphadolone (Althesin), minaxolone, pregnanolone (eltanolone), and the modern veterinary and human neurosteroids alfaxalone, brexanolone, and ganaxolone.

Within anesthesiology hydroxydione holds an honored place as a first-in-class agent and a proof of concept rather than as a practical drug. It is consistently cited in modern reviews of neuroactive steroid anesthetics as the pioneering compound that demonstrated a rationally designed steroid could produce safe, reversible general anesthesia, and it is credited with launching a lineage that leads to Althesin, alfaxalone, and the recently approved neurosteroid therapeutics.

Contemporary and retrospective appraisals are candid about why it failed in the clinic, namely its sluggish onset and its propensity to cause thrombophlebitis, and these liabilities are routinely used to frame the design goals of its successors. Outside professional and historical literature it is essentially unknown to the public, and it has no presence in the nootropic or supplement world; it is discussed here strictly as a landmark in the history of GABAergic anesthesia.