NOTE: Please, do not refer to the article it has been given as an arbitrary introduction to the question

I've stumbled upon an article daily heroin usage for 20 years. Basically, the article is describing a successful businessman who had been taking heroin multiple times a day for 20 years and had no side effects.

This is just an example of what I'm trying to ask.

My question is: Why do some people react badly to some drugs/medication while others take them like candies with no side effects?

Is it just genetics in action for some people which prevent reactions in our body or is it something else?

  • 4
    The question is interesting, but the example is off - medicines are intended to help and sometimes unfortunately have undesired effects (called side or adverse effects) when they are used. Heroin, on the other hand, is always abused; all effects that it has can be considered to be side-effects from a medical point of view. Note that mental health is also an important aspect of health - the addiction itself is a mental illness caused by heroin. In the article you linked: "I somehow manage to function. [...] I despise being an addict."
    – Lucky
    Nov 6, 2016 at 13:55
  • 5
    Since this question has now been bumped with a bounty, I'll reiterate what Lucky said over two years ago: There is no evidence in this article that this person experienced no "side effects" even if you treat heroin as a pharmaceutical that causes euphoria or pain relief or something similar as a primary intended effect. Quite the opposite: the article describes several side effects this person experienced. I would vote to close this question but can't because of the bounty.
    – Bryan Krause
    Dec 21, 2018 at 20:44
  • 1
    This is incredibly broad, yet interesting, and lacking – under current guidelines – more prior research. If you @someone could add either more "prior research" or "narrow down" the Q I would be all game for it. In fact I am already now, but please try one of the two mentioned alternatives first. (One imperative would be to better define "drug"!) Dec 21, 2018 at 22:53
  • 3
    @someone If you aren't asking something relevant to the example, don't use it as the example, it changes the meaning of your question. If I said "I'm really in the mood for something hot right now, like a cup of tea" I wouldn't expect other people to offer me a chili pepper.
    – Bryan Krause
    Dec 21, 2018 at 22:57
  • 2
    This is borderline impossible to answer in a general sense. Fact is, pure, pharmaceutical grade heroin taken under a doctor's supervision has surprisingly few side effects and could be taken for years without harm. It's not the horror drug people imagine. What makes it a horror is the fact that it's illegal and all that brings to the table. With other drugs, however, that's not true. There are many perfectly legal drugs that can have horrific side effects in weeks or months. So how to answer the question as stated? I don't think it can be answered. Every drug will have a different answer.
    – Carey Gregory
    Dec 22, 2018 at 23:13

2 Answers 2


Most drugs have wanted (main) and unwanted (side) effects, but neither of them are guaranteed. For example, aspirin may or may not relieve your headache and may or may not upset your stomach.

The lists of drug side effects base on decades of studies and consumers' reports, such as FDA (US), YellowCard (UK), Adreports (EU) and Medsafe (NZ), but if, let's say, ibuprofen has 100+ reported side effects, you as a single user will likely experience only few, if any.

The differences in side effects can depend on:

1. Drug factors:

2. Personal factors:

  • Genetics (body size, high threshold for side effects) can greatly affect your susceptibility for side effects.
  • Developed tolerance (metabolic or behavioral) to alcohol, cocaine, heroin, morphine or marijuana can greatly decrease their adverse effects (Drug Abuse).
  • Empty stomach is often more prone for irritation by a drug.
  • The social atmosphere in which the drug, such as alcohol or ecstasy, is taken can significantly influence side effects.
  • Initial psychological state in which one takes a drug: if worried, alcohol may make you more worried; if relaxed, it will likely make you more relaxed.
  • Allergy to a drug
  • Liver or kidney disease can slow down the breakdown of a drug and increase its side/effects.
  • Drug-disease reactions: Aspirin given to children with a viral infection, such as chickenpox or flu, can cause a fatal damage of the liver and brain (Reye's syndrome).

The bottom line: A side effect is not necessary an inherent property of a drug.

Bonus: Side effects, interactions and contraindications of medications, supplements and herbs (MedlinePlus, Mayo Clinic, Drugs.com, DailyMed)


One of the major things about heroin is that it is metabolized by the body as morphine and, if this person in the throes of heroin withdrawal were given medication like methadone, it couldn't be done without medical supervision as these are both really powerful drugs. Did the article say anything about the patient's daily ANYTHING?

With the assistance of doctors and others they're not obligated to divulge - HIPPA, the Health Information and Patient Protection Act would prevent the magazine from posting without express permission from the subject written about, and by 'subject', I mean the patient, not the point of the article.

That said, everyone has a different constitution regarding narcotics and other drugs. For some, the first exposure is deadly (chloroform, for example), others can handle much bigger exposure to multiple drugs because their constitution has been 'amped up', let's say, by usage of other drugs that we know nothing about, especially since no one can force a patient to be completely honest about their drug intake for any reason, nor is it a good idea to take someone else's word at the drop of a hat because people can simply write down their lies.

It's entirely possible that the businessman experiences withdrawal symptoms that are very well hidden by other drug use, or sedatives like the aforementioned methadone, especially if the patient is as heavy a user as you state.

  • 1
    This doesn't answer the question because the question isn't specifically about the example given. The question is more general and is summed up in the bolded sentence.
    – Carey Gregory
    Dec 23, 2018 at 23:54
  • Nevertheless @CareyGregory, the 2nd to last paragraph does help to explain the issue in the generalised question. +1 upvote from me Dec 24, 2018 at 12:16

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