In order to half the administered dosage of an oil-based time-release intramuscular injection, does that also require halving the time between dosing?

For example, if the initial dosing was:

1ml = 5mg weekly

and the quantity is divided in half to 0.5 ml, would that require the new frequency to be

.5ml = 2.5mg twice weekly

or

.5ml = 5mg twice weekly

or

.5ml = 2.5mg weekly

closed as off-topic by Narusan, DoctorWhom, Carey Gregory, Bryan Krause, Chris Rogers Sep 16 at 10:51

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  • Not sure, but I think you're going to have to name the drug. – Carey Gregory Sep 14 at 1:12
  • 3
    Say you have this prescription: 1ml = 5mg for 1 week And you halve it to 0.5 ml You don’t. You have been prescribed 1ml/w by your doctor, so it is really unrecommended to change it to anything. Call your doctor’s office and check with them, or at least ask the pharmacist. – Narusan Sep 14 at 8:58
  • @Narusan I agree and that's what I always do, go strictly by doctors orders, however the situation is a lot more complicated than that and if it were that simple I never would have asked. For privacy reasons and to skip a rather long discussion I'm just looking for an answer otherwise I'm left to figure things out without any help which in my case would be half it and see what happens. – June Sep 14 at 12:00
  • 3
    You can ask a pharmacist by calling a pharmacy. We can't give advice on changing medication dosing/administration for sure on this site. Either way, even if this question were hypothetical, I do not think there's an active pharmacist on this site right now and it's not something taught in med schools anyways. I would NOT make changes to weekly injections without discussing it with an expert. – DoctorWhom Sep 14 at 14:28
  • 3
    I second the recommendation to talk to a pharmacist. That's part of their job. – Bryan Krause Sep 14 at 15:43
up vote 4 down vote accepted

The intramuscular injection has rather erratic pathways of a drug absorprtion. Moreover the drug absorptions rate depends on a drug type and a target organ.

However for a purpose of illustration of the point raised by OP a simple pharmacokinetic model (y-axis - concetration, x-axis - time in hours) could be considered: pharma

You can see that the amount of drug injected takes roughly the same time to absorb for different concentration values.

As an answer of the OP's question, halving the administrated drug dose will not halve the inter-administration periods. For further details please consult Pharmacokinetics

  • Thank you, I had come to a similar same answer but this is a much better way of explaining it. – June Sep 15 at 13:19

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