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I would say from my limited prior research that the difference between a general numbing agent or a general anesthetic to an analgesic (or "painkiller") is that the former prevents the firing of nociceptors and the latter rather prevents one or more functions of a nociceptor (but not its ability to fire), causing it to fire weaker or, otherwise, interfering its signal.

My problem

I might totally misunderstood something along the way.

Furthermore, the 4 groups might be synonymous.

My question

What is the essential difference between a general numbing agent or a general anesthetic to a general analgesic (or "painkiller")?


Update

My understand from Brain Krause's great answer:
Hello, thanks for the great answer; I would say that the main thing I wanted to learn is "what is a general numbing agent that would make a man painless or lack pain totally but totally consciousness" and I understand that the correct term is a "powerful enough analgesic (or such preparation) that as of January 202 might not have been discovered yet".

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  • I think "pain killer" is too general and informal to generate a useful distinction because it has no medical definition, and it's really hard to compare general anesthesia (which produces reduced consciousness) to things that merely mask pain, but I've reopened your question nonetheless. When you're asking language questions it's very important to be very precise in the usage of the language. – Carey Gregory Jan 28 at 1:12
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The only one of those categories that should get the "general" modifier is anesthetic - this is to contrast them with local anesthetics, which are the "numbing agents" you describe.

General anesthetics

General anesthesics are agents that cause loss of consciousness. They prevent conscious perception of pain by causing loss of consciousness, rather than impacting pain pathways directly (some can also have direct analgesic effects, but this is not part of being a general anesthetic). It is still possible under general anesthesia for other systemic responses to pain to occur, and painful stimuli can cause arousal under lower levels of anesthesia. Therefore, general anesthesia is typically used alongside other methods for pain reduction.

There are several classes of general anesthetic. Commonly used are inhaled anesthetics like sevoflurane, intravenous anesthetics like propofol, and ketamine (which is a bit atypical). The mechanism by which general anesthetics causes loss of consciousness is a current area of research without clear answers, even though more is known about the molecular targets.

Local anesthetics

The drugs you call "numbing agents" are called local anesthetics. Local anesthetics block neuronal activity - they aren't particularly specific in a pharmacological sense. Instead, they gain specificity for pain by local administration.

The canonical class of local anesthetics are the '-caine's. Consumers are likely most familiar with lidocaine (available in over-the-counter creams for topical use) and procaine/Novocain (common in dentistry), but many other derivatives are used. Cocaine is also in this group, though typically used as a drug of abuse for other reasons, rather than as a local anesthetic.

The shared mechanism of these drugs is a block of sodium channels, which prevents neurotransmission. Local anesthetics can be applied topically, to target pain receptors, or can be injected in the vicinity of a nerve to block sensory neurotransmission through that nerve. Epidural anesthesia, such as used during child birth, is a particular use of local anesthesia targeted to the spinal cord.

Analgesics

Analgesics ("painkillers") more selectively target pain pathways. There are several classes, most medically relevant are the opioids, NSAIDs, and paracetamol/Tylenol. Opioids primarily target pain through inhibition of mu-opioid receptors; NSAIDs and related drugs through inhibition of COX-1/COX-2 and suppression of prostaglandin synthesis; the mechanism of paracetamol in pain relief is unknown.

Caveats

Of course, all these drugs have affects on other systems, as well. Opioids in particular are not themselves typically considered general anesthetics (high doses can cause loss of consciousness, but the margins for safety are not acceptable for most purposes), but can aid in general anesthesia. The classification into these three categories is about the primary mechanisms of action at the doses they are used.

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  • Hello, thanks for the great answer; I would say that the main thing I wanted to learn is "what is a general numbing agent that would make a man painless or lack pain totally but totally consciousness" and I understand that the correct term is a "powerful enough analgesic (or such preparation) that might not have been discovered yet". – user8225 Jan 28 at 22:21
  • @JohnDoea Do you mean a systemic drug that would block all pain, without affecting consciousness? No, there is no such drug. And likely given the severe negative outcomes in people who genetically cannot feel pain, such a drug would probably not be desirable. Opiods in a hospital setting can get pretty close, though, for short periods of time at least, but it wouldn't be correct to say they do not affect the level of consciousness. They also do not "numb" in the same way that local anesthetics do. – Bryan Krause Jan 28 at 22:25
  • Bryan, yes, that's exactly what I meant but you might interpreted me a bit further or I did a lousy job explaining myself --- I don't mean for such drug as a recreational drug in any way, I mean for it as a medical substance per se. I think it can be good to give such a generally harmless pill before any medical intervention such as minor surgery instead injecting tons of lidocaine in painful injections, for example; I believe a synergistic preparation would be avilable in about 40-50 years from now ; but that's just philosophizing for a moment. – user8225 Jan 28 at 22:30
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    @JohnDoea Yeah, there is nothing that can beat local administration of local anesthetics for true numbing for now. Typically the injections should not be particularly painful, for example it is possible to use topical anesthetics to minimize injection pain, or mild sedatives. Additionally, it is often not necessary to inject a large area, because injections are targeted to particular nerves instead, referred to as a nerve block. – Bryan Krause Jan 28 at 22:40

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