【藥事知多D】止暈藥知多D：Betahistine

今次藥罐子主要跟各位看倌分享Betahistine這種止暈藥。
　　
在藥理上，Betahistine是組織胺(Histamine)的冒牌貨，同時既是H1受體致效劑(H1 Agonist)，又是H3受體拮抗劑(H3 Antagonist)。
　　
雖然暫時還是不太清楚具體的作用原理，不過一般相信Betahistine可能會舒張前下小腦動脈(Anterior Inferior Cerebellar Artery, AICA)的血管，便可能會增加耳蝸血流量(Cochlear Blood Flow, CBF)，從而可能會紓緩梅尼爾氏症(Ménière’s Disease, MD)（俗稱「耳水不平衡」）的症狀，例如眩暈(Vertigo)、耳鳴(Tinnitus)。[1]
　　
在副作用上，主要是頭痛、皮疹(Rash)、腸胃不適。
　　
除此之外，還有一個非常詭異的副作用。
　　
這便是……
　　
噁心。[2]
　　
說到這裡，各位看倌可能會疑惑道：
　　
「嗄？藥罐子！很多藥都可能會誘發噁心喇！這有什麼好詭異呢？……咦？慢著……」
　　
對，聰明的看倌可能已經發現噁心其實也是其中一個耳水不平衡的症狀！
　　
這就是說，用藥者往往未必可能會察覺得到這種副作用。
　　
因為服藥前，這便可能已經出現了……

（如欲了解更多用藥資訊，歡迎看看「小小藥罐子」網誌。）

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著作➡️藥事知多D、用藥知多D、藥房事件簿、家居用藥攻略（各大書店有售）

Reference:
1. Laurikainen E, Miller JM, Nuttall AL, Quirk WS. The vascular mechanism of action of betahistine in the inner ear of the guinea pig. Eur Arch Otorhinolaryngol. 1998;255(3):119-23.
2. Lacour M, van de Heyning PH, Novotny M, Tighilet B. Betahistine in the treatment of Ménière’s disease. Neuropsychiatr Dis Treat. 2007;3(4):429-440.

多謝呢位醫生既分享
祝願周同學大步擸過😭😭😭😭
同時強烈譴責港警每次出動都不斷攻擊市民頭部！！直接造成嚴重傷害！！！
解散警隊！刻不容緩🖕🏿🖕🏿🖕🏿🖕🏿🖕🏿🖕🏿
#願榮光稱香港
#一齊集氣
#香港人不能麻木

[腦疝]

喺講腦疝之前，希望大家為周同學祈禱打氣，希望佢可以大步檻過。呢篇比較深，但希望大家可以睇哂佢。之前講過嘅腦硬膜外出血 (epidural haematoma)，以及腦硬膜下出血 (subdural haematoma)、蛛網膜下出血 (subarachnoid haematoma)，致死嘅原因都可以係腦疝。

疝，指器官受外力影響、而被迫入偏離本身位置嘅空間。腦疝，就係大腦或者小腦因為顱內壓上升，而被迫出本來嘅位置。

如圖，大腦同小腦由唔同嘅結構分開，形成唔同區域：大腦鐮 (falx cerebri) 分開左右兩邊大腦半球，小腦幕 (tentorium cerebelli) 將大腦半球與該邊嘅小腦半球分開。當顱內壓急速上升時，大腦小腦就會由原來嘅區域，被外力「啫」去另一區域，形成腦疝，從而壓住其他結構。

腦疝可分為四類：
一．大腦鐮下腦疝 (subfalcine herniation)。呢種腦疝嘅臨床病徵較輕微。通常嘅後續係大腦前動脈 (anterior cerebral artery) 比腦疝壓住，形成缺血性中風。
二．中央腦疝 (central herniation)。腦幹被外力向下壓，引起徵狀。最常見係第六腦神經 (外展神經, abducens nerve) 麻痺，引致斜視同埋複視。
三．顳葉鈎回腦疝 (uncal herniation)、亦稱小腦幕切蹟疝 (tentorial herniation)。指大腦顳葉 (temporal lobe, 旁邊靠近顳骨的部分) 中嘅鈎回 (uncus) 結構受壓而被擠出小腦幕。病徵有三：瞳孔擴大、郁唔到隻眼 (第三腦神經 (動眼神經, oculomotor nerve) 受壓麻痺)；半身不遂 (大腦腳 (cerebral peduncle) 受壓，其中嘅下行運動神經亦受牽連)；昏迷 (中腦網狀系統 (midbrain reticular formation) 結構受損)。大腦後動脈 (posterior cerebral artery) 亦有機會受壓，形成缺血性中風。
四．小腦扁桃體疝 (tonsillar herniation)。當壓力夠大，小腦可由枕骨大孔 (foramen magnum) 外疝。咁就嚴重啦，因為腦幹會因此受壓，其中控制呼吸同心跳嘅中心會受損，導致呼吸停頓、心跳停頓、血壓不穩，繼而死亡。

任何頭部創傷都可能引起顱內出血，繼而使顱內壓上升，最後腦疝。腦疝係可以致命嘅。所以希望大家為周同學打氣之餘，唔好忘記暴政曾經無數次向人民嘅頭顱攻擊，嘗試奪去我哋嘅性命。但係筆者亦都喺到呼籲：大家唔好絕望、唔好麻木，因為咁樣無異於自己用手向嘅頭顱使出致命一擊。要「毋忘初衷」呀，我哋繼續行落去啦。

***

[Brain herniation]

Before all, please pray for Mr. Chow - may he be safe and sound. The content of this post is a bit advanced, but I hope you can take some time and go through the whole passage. Conditions like epidural haematoma, subdural haematoma and subarachnoid haematoma can all lead to brain herniation, a serious and possibly fatal condition.

Herniation is the phenomenon where an organ is pushed to another location due to external pressure and forces. Brain herniation occurs when intracranial pressure (ICP) increases, and the brain parenchyma shifts its location.

As in the figure, we can see that the cerebrum and cerebellum are situated in different compartments, separated by different structures. The falx cerebri separates the bilateral cerebral hemispheres, and the tentorium cerebelli separates the cerebral hemisphere from the ipsilateral cerebellar hemisphere. When ICP increases, these structures will herniate into different spaces, compressing other structures.

Brain herniations can be categorised into 4 types:
1. Subfalcine herniation. Clinically this type of herniation has less symptoms. The major sequelae would be compression to the anterior cerebral artery, leading to ischaemic infarcts.
2. Central herniation. Downward compression to the brainstem leads to symptoms like strabismus and diplopia due to abducens nerve palsy.
3. Uncal / tentorial herniation. The uncus in the temporal lobe of the cerebrum are compressed and herniates through the tentorium cerebelli. Clinically there is a triad of symptoms: pupil dilation and progressive loss of eye movements (due to oculomotor nerve palsy), hemiparesis (compression to cerebral peduncle, damaging the descending motor neurons inside) and coma (damage to midbrain reticular formation). The posterior cerebral artery may also be compressed and cause ischaemic infarcts.
4. Tonsillar herniation. When ICP increases drastically, the cerebellum can herniate through the foramen magnum out of the skull. This is an extremely severe condition, in which the brainstem will be compressed, compromising its respiratory and cardiovascular control centres. This results in respiratory and cardiac arrest, fluctuation in blood pressure, and ultimately death.

Any trauma to the head can lead to intracranial haemorrhages, and that can lead to increased ICP and brain herniation, which may be fatal. We should not only pray for Mr. Chow who is suffering so much, but also remember how this government had aimed and shot at the heads of the people, trying to kill us. But it is unwise for us to be overwhelmed with hopelessness and numbness - that is even worse than a physical hit to your head! Never forget why we started - and let us walk further from here.

Figure adapted from Blumenfield H. Neuroanatomy through clinical cases, 2nd edition. Sinauer Associates, Inc. 2010.

澳洲神經學家George Paxinos
發現隱藏在腦中的新區塊！🧠

《Endorestiform Nucleus》
三十年前，科學家就認為可能有此區塊的存在，隨著科技的進步，才終於從影像和染色技術成功的發現。

它的位置位於下小腦腳(inferior cerebellar peduncle)，靠近腦和脊髓的連結處，取名為《Endorestiform Nucleus》
主要的功能是將人的感覺和動作做結合，像是姿勢、平衡、和精細動作。

很有趣的是在一些猴子或者他們研究的動物當中，是找不到這個區塊的，這也可能是為什麼人類的腦是這麼特別的！

這樣的發現，對於帕金森氏症和神經動作方面疾病的研究，可能將有更大的突破。
科學家說，這樣的發現就像在浩瀚的宇宙中發現一顆新的星星～🌟