Recent comments in /f/askscience

ferrouswolf2 t1_j6g6mcz wrote

Reply to Can you (roughly) determine the dosage of a drug taken based off of the blood concentration? by bynarie

For a process like this you’d need to have data from studies (like clinical trials) to compare against. You couldn’t a priori take an arbitrary drug and back calculate. For instance, some drugs require a biotransformation to become reactive. Some may be bound and metabolized in a certain organ, and still others may have a short half life.

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bruce_kwillis t1_j6g027h wrote

Reply to comment by TheRedLob in Can you (roughly) determine the dosage of a drug taken based off of the blood concentration? by bynarie

To add in, at least in the US it's a little less to do with the therapeutic range and a whole lot more with the safety range,and what was tested during clinical testing.

Since we often look at log differences in the clinic when it comes to safety, you can safely assume for most drugs prescribed at x mg/day that they will still be efficacious in a fairly large range of adult weight ranges.

However, especially with some drugs as you have indicated, this isn't the case. Personally I am often worried with something like hormonal birth control, which we are constantly trying to reduce the dose to limit side effects, however there is efficacy issues with larger patients.

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azuth89 t1_j6fth5o wrote

Reply to comment by hypatia_knows_best in What makes it difficult to determine whether nutrient deficiencies are implicated in mental-health issues like ADHD? by LinguisticsTurtle

Right, which they do by combing through existing records and looking for correlation. Covered that.

I didn't say nothing could ever be done or studied, I said controlled experiments are very difficult on multiple levels and they're often leaning on data from other sources. That leaves gaps in what can be studied, but paternal age isn't one of those in many places.

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TheRedLob t1_j6frjrr wrote

Reply to comment by r7-arr in Can you (roughly) determine the dosage of a drug taken based off of the blood concentration? by bynarie

Yes! In general, you cannot bring a drug to market without being able to measure it in blood reliably. But those tests are often not available in eg a rural hospital. This field is therefore a real interplay between doctors, statistici an/software engineers, and bio-assay manufacturers.

Now for illegal designer drugs, that is a completely different ball game. They may even be built to evade detection.

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TheRedLob t1_j6fqqwt wrote

Reply to comment by Optimistic__Elephant in Can you (roughly) determine the dosage of a drug taken based off of the blood concentration? by bynarie

Some drugs are!

Drugs that work with a single dose for everyone are more convenient. Yes, paracetamol 1g tablet may give lower concentrations in someone weighing 140kg vs 70kg, but these drugs are safe and effective over a wide range of concentrations.

Some drugs have a more narrow therapeutic range. We either adapt the dose by bodyweight (paracetamol for children is a prime example!), but can adapt to many many more covariates. Even race can play a role, with some mutations increasing drug metabolism being less prevalent in whites, so more risk of overdose. And sometimes, it is not the dose but the frequency that is adapted (1g 2 times vs 3 times per day)

In some cases, no covariates exist. You either measure concentration in the blood, or you measure the effect (eg drugs for sedating during surgery).

Sure, it would be more optimal to also dose paracetamol that way. Dose high,measure concentration in blood and adapt. You would get faster pain relief with lower risk. But would you come to hospital and pay a team of doctors/engineers to do that, for a simple headache?

That was the question I answered with my PhD: is all that hastle worth it? For some life saving drugs with strong side effects and very variable metabolism, it is.

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rootofallworlds t1_j6fo9s4 wrote

Reply to Is there an upper limit to structure size in a vacuum? Could a sufficiently advanced civilisation build a galaxy sized structure in space or would it become too massive and collapse in on itself? by CubanHermes

All materials have structural limits. A column, made of a certain material in a certain gravitational field, will either crush or buckle under its own weight if it is too high. This still applies if the gravitational field is the self-gravity of the structure itself.

Dynamic support might be used. One concept is you make a sort of long skinny particle accelerator and the particles going back and forth exert a reaction force on the endpoints supporting the far end. But even with that, the bottom end loop has to be able to support the load.

Based on known materials, even a solid Dyson sphere is impossible without dynamic support. A realistic Dyson sphere would instead be simply a swarm of satellites so dense it can absorb nearly all its star's light.

The ultimate limit is that the volume of a region of space scales with radius cubed, but the critical mass above which a black hole is formed scales linearly with radius. Thus the larger a structure is, the less dense it must be to stay below that critical mass. (Which in any case could only be approached by transporting matter in from other galaxies, since the starting galaxy was obviously not a black hole.)

Once you're at the point that the "structure" is a thin mesh of wires or tubes stretching over interstellar distances, well, why have the structure at all instead of just a bunch of free-floating spacecraft that can share power and data with lasers or something?

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