AboutBarbara Judge Expertise Outpatient pharmacy and general health. I have recently completed a Pharmceutical Care Certificate Program offered by Purdue University (Spring 1999 completion). I have personal experience dealing with terminally ill persons and their needs, as well as their families` needs. I graduated in 1984 from Pharmacy School and have been a Licensed Pharmacist since then. I have 18 years retail pharmacy experience. Prior to my pharmacy training I have 3 years hospital experience as a Nurse`s Aide.
1. What is the half-life of a medication?
2. Is there a "general rule" for determining how long a medication will stay in your system (I know in the old days, we used to hear you needed to detox for three full days to eliminate most narcotics before you could expect to have a clear drug screen -- and that was if you were NOT a chronic user)
I need to understand this before I can get to the question I really want to ask.
Thank you.
ANSWER: 1. The half-life of a medication is the time it takes for your body to metabolize and excrete a drug so that half of the drug is removed from your body.
2. As a general rule you are considered fully clean in blood and urine after 5 half lives. Keep in mind that the half of every drug varies greatly. Half life can also vary from patient to patient if the patient suffers from altered kidney or liver function.
If you want complete information on drug screening, the most complete and accurate source of information I have found is www.erowid.org. This website lists commonly performed tests, time frames for one time users, long term users, and drugs or other products that cause false positive tests. It is the best source I have found. Any question you ask me I will most likely reference that website if I don't know the answer.
Thanks
Barb Judge
---------- FOLLOW-UP ----------
QUESTION: hanks for the referral to erowid! I am actually working toward increasing the medicatation level rather than detoxing, so I'd like to run this past you first, and if better to ask elsewhere, thank you for referring me again.
I want to figure out how many 30mg ms contin tablets one would have to take to achieve the expected results from an IV in an ICU at the following strengths:
1. 2 mg/h 24 times each day (for 6 days) = _____
2. 10 mg/h 24 times each day (for 1.5 days) = _____
3. 10 mg/h every 15 mins for 1:15 (5 total) = _____
Point of the exercise is that I can relate to 30mg pills but have no experience with parenthal doses.
My husband was prescribed 3x30 mg ms contin 2 times/day for arthritis BEFORE an accident landed him in ICU. For the first six days, he received 2mg/h morphine sulfate through an IV. On Day 6 it was increased to 10 mg/h. Late on Day 7, his blood pressure crashed. He continued to receive 10 mg/h every hour until early on Day 8 when a dose was delayed a half hour. When it resumed, a 10 mg/h dose was given every 15 minutes (5 total in 1:15). He was then subjected to an apnea test which he failed due to no spontaneous breathing.
In the beginning, I thought he needed more pain relief and asked the Resident MD how the 2mg/h compared to the dose he was getting in his pills. He checked with the hospital pharmacist and told me, "they are about the same." Later, I asked an anesthesiologist, not involved in my husband's care if he had a formula. He said, that as a baseline, one could use a "3:1 ratio" oral to IV. I asked our regular pharmacist who told me there are entirely too many variables involved for him to attempt to answer.
The information provided by the hospital seems to match the information provided by the anesthesiologist with the following equation. In this case, it errs on the conservative side and that makes sense.
ORAL: 3x30mg 2x day = 180mg every 24hrs
PARENTHAL: 2mg/h x 24 = 48 x 3 = 144
If I go forward with this equation, then when the dose increased to 10mg/h, he would have had to take 12ea 30mg pills twice a day to get the same affect. And in that last 1:15, he would have had to take something like 112 30mg pills over the course of 1:15 to achieve the same results. Somehow I seem to be calculating something wrong.
Please help.
Thank you,
Theresa Roberts-Wall
Answer To start with, the anesthesiologist you spoke with is correct. The conversion factor of morphine he gave you 30mg oral is equal to 10mg IV is correct. Second, I don't understand why your husband's morphine was increased so greatly AFTER his blood pressure crashed, and why that dose of morphine would be continued after he failed an apnea test. If this was a family member of mine I would be posing some serious questions to the staff about continuity of care. Here are the calculations I came up with.
Days 1 thru 5: 2mg/hr X 24 hr = 48mg IV. (equivalent to less than his normal home dose and probably not enough morphine to help acute pain from an accident on top of his "normal" level of daily pain.
Days 6-7: 10mg/hr X 24 hr = 240mg IV. (720mg oral est.) This is 4 times his home dose.
Day 8 and beyond: 10mg/15mg X24 hr = 960mg IV (2880 oral est.)
This is a huge increase in a short period of time. I would consult with his doctors as soon as possible.
