Sternmeadow Tea Poisoning

Sternmeadow Tea is an uncommon medicinal beverage derived from the Sternmeadow plant, and is sometimes referred to as “anti-alcohol,” though the comparison is inexact. It is used as a calming agent, work aid and occasionally as the vehicle for pranks. Ingesting too much of the substance can be toxic, but it is safe in low doses.
Appearance:
Sternmeadow plants are small, purplish green growths with a central stalk leading to three leaves that curl slightly upwards at the edges, seeming to form a small depression or valley. They grow predominantly in temperate climates in the shadow of trees, where they acquire water by tapping into the root systems of larger organisms. Sternmeadow plants are fairly easy to identify during the day due to their coloration, but gathering them by night can be difficult, as their shape is similar to that of common ivy.

Effects:
If Sternmeadow plants are consumed raw they leads only to severe nausea, but when brewed into tea they are known to have a very specific psychological effect on most sapient humanoids. Those who consume the tea begin to lose their sense of humor, spontaneity, creative drive and flexibility of mind.
The effect grows more pronounced the more of the tea one consumes, leading from the mild stoicism of a single cup all the way to full intoxication, where the subject loses almost all ability to have fun, allow their mind to wander or think creatively about solving problems. Those who are “overstern,” have difficulty with metaphorical language and consider jokes a waste of time. They are often hyperfocused and can be almost dogmatically literal about following whatever rules or procedures they believe to be appropriate. Note that the tea does not convince them to follow any rules in particular, it simply makes them inflexible regarding the ones they already observe. Thus, those intoxicated by the tea also tend to be difficult to convince of anything they do not already believe. It is possible to "overdose" on the tea, leading to fainting episodes and symptoms similar to obsessive compulsive disorder, but this rarely occurs as the tea is so bitter that it's difficult to unknowingly ingest very much of it.
The Tea's nickname results from how these symptoms contrast with alcohol, known for increasing spontaneity, lowering inhibitions and in some cases causing apathy, mood swings or euphoric episodes. Actually combining alcohol with the tea is extremely dangerous however, as together they are highly toxic to most humanoids, and drinking both substances within the space of an hour will deal poison damage.
Uses:
In medicine, Sternmeadow Tea is often used to treat hysteria, mania and various forms of temporary madness. It is sometimes used as a supplement by guards or watchmen, as it is slightly more effective than caffeine at keeping one awake and alert, and some guards believe it helps cultivate a certain no-nonsense attitude towards their profession. Some watchmasters have even been caught slipping some of the tea to particularly lackadaisical young recruits, though such practices are technically illegal throughout most of the continent. Dosing someone without their knowledge is actually quite difficult, as it has a strong, bitter taste that cuts through most other flavors, but it is possible to conceal if mixed carefully with certain herbs.
In Culture
In mild doses, the effects of the tea can be difficult to distinguish as unusual unless the observer has a history with the subject, so its use is not readily apparent. Complicating matters, there exists a small but dedicated subculture of Sternmeadow Tea enthusiasts, and some bars in larger urban areas provide the tea to those who want a little help maintaining their gruff and dour demeanor. Depriving such a person of their tea after they've grown used to a regular dose can lead to outbursts of silly, impulsive and nonsensical behavior.

Symptoms

Ordinary levels cause a slight feeling of warmth and tend to mildly slow blood circulation, which can lead to skin becoming unusually pale. 
In doses high enough to be toxic, pupil dilation, muscle tics and a sour feeling in the back of the throat are common.  A common diagnostic test is to see if the patient remains capable of telling a joke.

Prognosis

Sternmeadow tea leaves the system naturally after a few hours, but it is difficult to remove from the body prematurely with means short of magic. Very skilled herbalists and alchemists might know that a remedy exists that can accelerate this process, but cases of Sternmeadow poisoning are so few and far between that there's rarely a need, and only very well-trained or well-informed apothecaries will know what to do if someone overdoses.

Cultural Reception

Sternmeadow tea features prominently in idioms meant to imply that someone takes things too seriously or needs to lighten up. "Who sterned your tea?" is a common response to behavior that's perceived as overly dogmatic or anal retentive.

Type

Neurological

Rarity

Uncommon