Prototype antidote
Antidote (prototype) is a type of antidote meant specially for Shinichi to revert the APTX 4869's body-reducing effects temporarily. It was created by Shiho Miyano, the original creator of the APTX 4869, who used baiju (Chinese alcohol) as a main ingredient after Shinichi had told her about the baiju's effects.
Contents
Description
It is widely known that Shinichi has taken this antidote a number of times, usually twice every few hundred cases, occasionally that means, and the effects remain: back to Shinichi for 24 hours, return to Conan. Second dose: back to Shinichi for shortened time.
Many fans guess that this antidote made by Ai is not a prototype, but fully developed, with time limit side effects. This might be true, and the most likely reason she refrains from letting Shinichi take a lot or refrain from taking them herself is so they can stay away from the Black Organisation until they find a way to liquidate the syndicate.
Main ingredients
Other than extracts of baiju, not much is known about the antidote's ingredients. However, Shiho once mentioned about some parts of the APTX 4869 being added.
Usage
According to Shiho, the first dosage will have its effects last for 24 hours, but the next dosage will be much shortened, due to the harmful chemicals in the antidote being recognised by Conan's immunity system. These two-dosage effects and side-effects stay consistent only if Conan takes them occassionally.
First time
When Ran had caught on to Shinichi's Conan identity secret, he had to find a way to make her think otherwise. Thus, Shiho (as Ai Haibara) helped him by coming up with an antidote, saying he had to take it at his own risk, because no one had tried it before - and hence he became the successful guinea pig. Ai went even further to dress up as Conan to appear at the same time with Shinichi, and Ran stopped suspecting him.[1][2]
Second time
The antidote prototype was again taken, this time accidentally in place of cough syrup. Luckily so, it seemed, because it was during a case where an enemy, in plastic surgery disguise as Shinichi, tried to implicate Shinichi. And since he had taken the drug, he could defend himself. It wore off 24 hours later, with Ai giving him another one to protect his identity. This time it wore off in a shortened 4 hours, once again interrupting the process of confession of feelings to Ran. The phrase of "It's always so close!" (which Gosho Aoyama uses quite frequently in love plots) can be read in the manga when he returns to his kiddo form of Conan.[3][4][5][6]
Holmes' Revelation
Most recently, in London, Conan is given the antidote so he can fly to London, because the alias Conan Edogawa does not exist and has no passport. Haibara passes to Conan a second pill for the trip back to Japan. However, after Conan accidentally reveals Shinichi is in London, Shinichi (as Conan) is chased by Ran, who doesn't know she is actually chasing Conan, but thinks it's Shinichi she chased. Conan hides in the booth and ingests the return-trip pill, and walks out of the booth. A bawling Ran runs away, and Shinichi runs after her. He grabs her arm and pulls her in front of him at the Big Ben, and this time nothing stopped him from confessing his feelings, somehow.
Fortunately for Shinichi, after he turns back to Conan and apprehends the terrorist together with Minevra Glass, his parents Yusaku and Yukiko appear, giving him the third pill under orders from Haibara. He then goes back to Japan.[7][8][9]
Other times
Haibara, due to not having a proper lab, cannot mass produce the antidote and thus, she makes mistakes sometimes and some of the antidotes Conan takes have very, very horrible side effects.
In most movies, taking the antidote will last the normal form of Shinichi for only at most two hours, and the one he took in OVA 9 made him fall into a coma, where he dreamt of him never being able to become Shinichi again, but remained Conan throughout ten years. When he woke up, he transformed back to Shinichi.
