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


.5ml = 5mg twice weekly


.5ml = 2.5mg weekly
  • Not sure, but I think you're going to have to name the drug.
    – Carey Gregory
    Sep 14 '18 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 '18 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 '18 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 '18 at 14:28
  • 3
    I second the recommendation to talk to a pharmacist. That's part of their job. Sep 14 '18 at 15:43

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 '18 at 13:19

Not the answer you're looking for? Browse other questions tagged or ask your own question.