Medicines and Doses

[ManjiB]

When I was at school, I wanted to become a pharmacist.
Unfortunately for me, this didn’t happen, but perhaps if I had become a pharmacist, maybe I would have known the answer to this …

It is my belief that when medicines are prescribed, whilst the medicines are available in different strengths, they are not “personalised”.

For example, let’s say I have a condition that needs a drug that is available in 5mg, 10 mg, 15 mg, 20mg and up to 50 mg.

Let’s say the doctor wants to start me off at the lowest possible dose which in this case is 5mg.

What does the doctor take into consideration what the dose for me should be?

Below is a table of average weights for male and females at 3 different heights.

Male Weight Chart by Height
Height in Feet	Height in cm	Average Weight Range in kg		Difference between low and high in kg
4’6” feet	137 cm	28.5 – 34.9 kg		60.4
5’3” feet	160 cm	50.8 – 60.1 kg
6’0” feet	183 cm	72.6 – 88.9 kg
Height and Weight Chart Female
Height in Feet	Height in cm	Average Weight Range in kg		Difference between low and high in kg
4’6” feet	137 cm	28.5 – 34.9 kg		51.3
5’3” feet	160 cm	47.2 – 57.6 kg
6’0” feet	183 cm	65.3 – 79.8 kg

Note The shortest person is 4’ 6" tall and the tallest person is 6’ 0" for the purpose of this illustration.

Note also the lowest weight is 28.5 kg and the highest is 88.9kg for male and 28.5 kg and 79.8 kg for female.

Difference between lowest and highest is 60.4kg in males and 51.3 in females.

Here’s what is puzzling me and it’s where perhaps a pharmacist or a doctor might have the answer.

Let’s say the smallest person and the biggest person are being diagnosed as needing this treatment and the lowest dose is 5mg. Is it the case that they both would get 5 mg prescribed?

This is my guess since I never see a doctor look up in a chart when they are prescribing medicines for me to see what my dosage should be for a male of weight x and height y (yet they do BMI calculations do they not?)

So how is it that two extremes of people (and also the genders should be considered) get the same dosage (that of an adult as children do indeed have different doses).

So in this example, a female of 4’ 6" weighing 28.5 kg and a male of 6’ 0" weighing 88.9 kg would both be given tablets of 5mg to treat their condition.

How does that work?

I mean we are told we should consume calories based on weight/size, so why does this rule not apply to medicines? Or does it?

This is a puzzle for me and I am sure that I am right in thinking that medicines are not prescribed in a tailor made fashion i.e. when I last saw my GP he gave me an “adult” dose which would the same he would give to any adult regardless of size or indeed age group.

Something to think about, or maybe not?

Any pharmacists or doctors want to chip in?

Namaste|

[Rups]

I thought medicine dosage was to do with metabolism and liver function? I don’t really know but I’d thought I’d be the first to reply to your post since my new kitten has got me up at 5:30 am.

I suppose it might have to do with the type of medication as well. I take an SRRI which has a dosage range from 20mg to 40mg for an effective dose and my partner takes an SRRI which has a dosage range of 50 to 100mg. Citalopram, the one I take needs to be administered in lower dosages as people age because it can cause an electrical disturbance in the heart at higher dosages. Whereas, Sertaline does not potentially cause this so it can be administered safely at higher dosages regardless of the weight, height or gender of a person but it can cause gastric problems so if someone has stomach issues, they would be put on a lower dose.

Anyhoo, that is my two pence worth on a subject I know very little about.

[Mrs5K]

I have no idea but I imagine the extent of your condition is also taken into account. E.g. if your BP is high they might alter the dose based on how high your BP is.

I have seen my Dr look things up before prescribing meds for me. Their experience may mean they don’t need to look.

Aa Rups has said I know very little about it either.

[BHAGYODAY]

As far as I know the infants,children get medicines as per body weight (LIKE MG/KG BODY WEIGHT),but for adults it is not so.FOR elderly medicine dosages may be lower because renal function is also considered due to delayed excretion of drug & its toxic effects,like some medicines for heart failure conditions are taken 5 days of a week & 2 days without a particular drug.

[Gnasher]

So far they have been right with any medication I’ve had to take in my life. So hopefully they are right with all the new medication since the stroke. But who knows. We can only hope they know what they are doing.