# Do all drugs have counterparts that have the opposite effect?
**URL:** https://boards.straightdope.com/t/do-all-drugs-have-counterparts-that-have-the-opposite-effect/607513
**Category:** Factual Questions
**Created:** [December 27, 2011, 1:25pm UTC](https://boards.straightdope.com/t/do-all-drugs-have-counterparts-that-have-the-opposite-effect/607513 "2011-12-27T13:25:00Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@robert\_columbia](https://boards.straightdope.com/u/robert_columbia)
#### Post date: [December 27, 2011, 1:25pm UTC](https://boards.straightdope.com/t/do-all-drugs-have-counterparts-that-have-the-opposite-effect/607513/1 "2011-12-27T13:25:00Z")
Pretty much as in the title. Are there drugs in existence (or drugs that are strongly hypothesized to exist) that do the exact or pretty close to the opposite of existing drugs? For example, one group of Antidepressants are known as “Selective Serotonin Reuptake Inhibitors”. These drugs supposedly lift mood. Are there drugs that specifically lower mood and/or mutually nullify the effect of antidepressants? E.g. perhaps a “Selective Serotonin Reuptake Accelerator”.
Don’t just say “depressants”, because those are central nervous system depressants, not mood depressants.
Other drugs are also in scope - for example, are there “propsychotics”, “proalgesics”, “protussives”, “mood destabilizers”, “beta battering rams”, or “prohistamines”?
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### Author:  [@johnpost](https://boards.straightdope.com/u/johnpost)
#### Post date: [December 27, 2011, 1:46pm UTC](https://boards.straightdope.com/t/do-all-drugs-have-counterparts-that-have-the-opposite-effect/607513/2 "2011-12-27T13:46:08Z")
organisms are complex biochemical systems with many types of feedback and control. pathways and processes can be be stimulated or diminished from their ordinary level, the system has chemicals for it.
systems will get affected without directly using a drug as well. you can remove a drug affecting a system and get a rebound taking that thing beyond a normal level in the other direction. some people might take an antihistamine for a cold and after the cold is gone and they stop taking the antihistamine get a rebound of histamine levels that is as high as the cold would have done (though maybe shorter).
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### Author:  [@mnemosyne](https://boards.straightdope.com/u/mnemosyne)
#### Post date: [December 28, 2011, 2:40am UTC](https://boards.straightdope.com/t/do-all-drugs-have-counterparts-that-have-the-opposite-effect/607513/3 "2011-12-28T02:40:13Z")
It’s very hard to design a drug - which is something which we’d have to master in order to be able to answer “yes” to your question.
Drugs come about mostly through observation of how animals (including humans) react to stuff. Historically, this “stuff” is largely plants and fungi and molds - we eventually identified the molecule that created a particular effect and called that a drug to treat X.
Further advances in drugs _tend_ to be either modifications to something like X, maybe adding or removing or slightly changing a functional group (a reactive chemical component of the structure) and seeing if that treats a disease/symptom better or worse than the existing drug. Perhaps the drug metabolism is such that it breaks the drug into two parts, and one part is prone to causing bad side effects… using incredibly simplistic examples, if you can take something that looks like a d and modify it so that it looks like an a, that could be an improved drug.
Using a random and not entirely thorough example off the top of my head:
Designing a drug to treat a particular disease involves knowing how a disease works…if you’re lucky, you have something like the CML leukemias caused by the [Philadelphia chromosome](http://en.wikipedia.org/wiki/Philadelphia_chromosome), you can identify a single protein/enzyme that needs to be deactivated, and you can find a drug that will do that. That doesn’t mean you can necessarily create something that will “just as easily” enhance/activate the protein (if you consider the original development to be “easy”).
If you’re unlucky -as is the case with most diseases you could name, and several more you couldn’t - there isn’t a single protein/enzyme or disease source that you can target in order to treat the disease, let alone conceive of a designed opposite.
This doesn’t address the idea of _why would you want to?_ Despite lots of web pages on the internet, most Big Pharma - and Small Pharma - researchers really do want to just treat diseases. It just isn’t all that simple.
And as **johnpost** said, you do have “opposite” effects and side effects. You can have “uppers” and you can have “downers” or you could have drugs that cause constipation and drugs that cause loose stools, and you could label those as opposites as you suggest in your OP, but there isn’t much point in doing so, other than perhaps recognizing that these effects can be used to balance a drug dosing regimen in order to minimize the side effects/suffering by the patient!
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### Author:  [@grude](https://boards.straightdope.com/u/grude)
#### Post date: [December 28, 2011, 8:52am UTC](https://boards.straightdope.com/t/do-all-drugs-have-counterparts-that-have-the-opposite-effect/607513/4 "2011-12-28T08:52:10Z")
Lets say a drug causes an effect because it has a molecule correctly shaped to lock into a receptor in the brain and activate it(these are called agonists) well there are also drugs which have molecules shaped slightly differently so that they lock into the receptor but do not activate it, and they also sometimes block any agonist from getting into the receptor too(these are called antagonists).
Most drugs with a psychoactive effect that are well known like opiates and methamphetamine work like this, see this article:
> **[Agonist](https://en.wikipedia.org/wiki/Agonist)**
>
> An agonist is a chemical that activates a receptor to produce a biological response. Receptors are cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an antagonist blocks the action of the agonist, while an inverse agonist causes an action opposite to that of the agonist.
> From the Greek αγωνιστής (agōnistēs), contestant; champion; rival \< αγων (agōn), contest, combat; exertion, struggle \< αγω (agō), I lead, lead towards, conduct; drive
> Receptor...
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### Author:  [@Fish\_Cheer](https://boards.straightdope.com/u/Fish_Cheer)
#### Post date: [December 29, 2011, 7:11am UTC](https://boards.straightdope.com/t/do-all-drugs-have-counterparts-that-have-the-opposite-effect/607513/5 "2011-12-29T07:11:11Z")
> [@robert\_columbia](#):
>
> Are there drugs in existence (or drugs that are strongly hypothesized to exist) that do the exact or pretty close to the opposite of existing drugs?
Two examples I remember from my pharmacology classes:
> [@](#):
>
> In biochemistry, cholinesterase is a family of enzymes that catalyze the hydrolysis of the neurotransmitter acetylcholine into choline and acetic acid, a reaction necessary to allow a cholinergic neuron to return to its resting state after activation.
>
> A cholinesterase inhibitor (…) suppresses the action of the enzyme. Because of its essential function, chemicals that interfere with the action of cholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death (examples are some snake venoms, and the nerve gases sarin and VX). One counteracting medication is pralidoxime.
> **[Cholinesterase](https://en.wikipedia.org/wiki/Cholinesterase)**
>
> The enzyme cholinesterase (EC 3.1.1.8, choline esterase; systematic name acylcholine acylhydrolase) catalyses the hydrolysis of choline-based esters:
> Several of these serve as neurotransmitters. Thus, it is either of two enzymes that catalyze the hydrolysis of these cholinergic neurotransmitters, such as breaking acetylcholine into choline and acetic acid. These reactions are necessary to allow a cholinergic neuron to return to its resting state after activation. For example, in muscle contrac...
> [@](#):
>
> Pralidoxime (…) attaches to the site where a cholinesterase inhibitor has attached, then attaches to the inhibitor, removing the organophosphate from cholinesterase, allowing it to work normally again.
> **[Pralidoxime](https://en.wikipedia.org/wiki/Pralidoxime)**
>
> Pralidoxime (2-pyridine aldoxime methyl chloride) or 2-PAM, usually as the chloride or iodide salts, belongs to a family of compounds called oximes that bind to organophosphate-inactivated acetylcholinesterase. It is used to treat organophosphate poisoning in conjunction with atropine and either diazepam or midazolam. It is a white solid.
> Pralidoxime, 2-pyridinaldoxime methylchloride, is prepared by treating pyridine-2-carboxaldehyde with hydroxylamine. The resulting pyridine-2-aldoxime is alk...
> [@](#):
>
> An opioid is a psychoactive chemical that works by binding to opioid receptors, which are found principally in the central and peripheral nervous system and the gastrointestinal tract. The receptors in these organ systems mediate both the beneficial effects and the side effects of opioids. Opioids are among the world’s oldest known drugs; the use of the opium poppy for its therapeutic benefits predates recorded history.(…) Opioids bind to specific opioid receptors in the nervous system and other tissues.
> **[Opioid](https://en.wikipedia.org/wiki/Opioid)**
>
> Opioids are a class of drugs that derive from, or mimic, natural substances found in the opium poppy plant. Opioids work on opioid receptors in the brain and other organs to produce a variety of morphine-like effects, including pain relief.
> The terms "opioid" and "opiate" are sometimes used interchangeably, but the term "opioid" is used to designate all substances, both natural and synthetic, that bind to opioid receptors in the brain. Opiates are alkaloid compounds naturally found in the opi...
> [@](#):
>
> Naloxone is an opioid antagonist drug (…) used to counter the effects of opiate overdose, for example heroin or morphine overdose. Naloxone is specifically used to counteract life-threatening depression of the central nervous system and respiratory system.
>
> Naloxone has an extremely high affinity for μ-opioid receptors in the central nervous system. Naloxone is a μ-opioid receptor competitive antagonist, and its rapid blockade of those receptors often produces rapid onset of withdrawal symptoms.
> **[Naloxone](https://en.wikipedia.org/wiki/Naloxone)**
>
> Naloxone, sold under the brand name Narcan among others, is an opioid antagonist, a medication used to reverse or reduce the effects of opioids. For example, it is used to restore breathing after an opioid overdose. Effects begin within two minutes when given intravenously, five minutes when injected into a muscle, and ten minutes as a nasal spray. Naloxone blocks the effects of opioids for 30 to 90 minutes.
> Administration to opioid-dependent individuals may cause symptoms of opioid withdrawa...