Why do some drugs stay in your body longer than others?

[ladypam]

Have you ever wondered what happens to that tiny pill which you have just put in your mouth and swallowed with a gulp of water? Probably not. All you were probably concerned with is how soon you will feel its actions taking effect in your body to give you relief from whatever is ailing you. But if you look closely, you would see that this small pill will first go to your stomach, to be digested first by the numerous substances and acids found there. Once the active ingredient of that pill reaches the intestines, it is then absorbed and goes to the liver for it to be metabolized. Some of its components become excreted in the urine, and the rest, after being broken down further into its active metabolites, will reach the blood vessels or get attached to proteins. From the blood stream, the unattached metabolites will then be directed to the target area. And this is the only time you will feel its effects.

Where does it go?

As you can see, most oral medications go through a lot of pathways first until it can reach its target area. And because of this, the amount that reaches the blood stream is just a percentage of what you took. This is what is known as bioavailability. Bioavailability can be defined as the percentage of a dose that enters the body. And this is quite significant in cases of overdose.

Medications given through the vein have a hundred percent bioavailability since they are directly given on the blood stream. But oral medications usually have less than a hundred percent. Medical practitioners and physicians are often aware of this and take this into consideration whenever they prescribe medications to their patients. It will help greatly in deciding the dosage to be given and what route to use for its administration. Overdose usually occurs when the dosage given intravenously is meant for oral use because of the levels of bioavailability.

How long does it stay?

Another point raised is how long does a medication stay in the body. One of the factors affecting this is the half life of the medication. This often dictates how long the medication will remain in the body before it is cleared and excreted as waste material or used up in metabolism. This also dictates how much or how often of the medication should be administered to a patient in order to reach a state of having steady concentrations of the medication in the blood stream. Having steady concentrations of the medication inside the body is tantamount to having that medication is effectively treating your condition. Don’t you ever wonder why your doctor always advises you to take your medications on time? The reason for this is that a certain concentration must be maintained in the blood stream to maximize the effects of the medication. Erratic levels may lead to a failure in treatment.

It is also quite important to know this whenever you plan to change or take a new medication. There are a lot of medicines that react adversely with one another and it is quite safe for you to get rid first of the previous medication before starting a new one. A good example for this is taking MAOIs and Benzodiazepines. You must be sure first that your body is rid of any trace of MAOIs before starting on a regimen of benzos or else severe side effects may occur.

What affects its stay?

As the effect of several medications varies with each person, there is not absolute way of telling how long a certain medication stays in the body. It is affected by the following factors:

* The different drug properties including solubility, state of being hydrophobic, pKa, etc.
* How the drug is formulated and manufactured, that is, is it made to be released at once, or released over a period of time, or released after a certain period of time
* The presence or absence of food when the drug was ingested
* Rate of the emptying of the stomach
* Differences in circadian rhythm
* Interaction of the drug with different enzymes, drugs, food
* What and how it is transported
* Condition of the gastrointestinal tract
* Differences in metabolism due to age and genetic makeup
* Condition or health of the entire body systems

Applications

Knowing all these can help you determine the presence or absence of certain drugs in the body. This is often a subject of importance whenever people are suddenly scheduled to have a drug test and may have taken a certain medication that may affect the results. They often think that since they have taken over a month before, they will not get into trouble because it has already left their system. Presented below is a list of common substances tested for during drug tests and their corresponding detection periods based on which type of drug test is given. These are approximate values, depending on how much was taken, how long it was taken, the body’s metabolic rate, age, body mass, urine pH, tolerance to the drug, and overall health.

* Alcohol can be detected within 12 to 24 hours in urine, but no data yet on blood, saliva, and sweat drug tests. It is not present in hair follicle drug tests.

* Amphetamines, including Biphetamine, Dexedrine can remain in saliva for 3 days, in urine for up to 4 days, and in hair follicles for up to 90 days. No data on blood and sweat tests.

* Methamphetamines, which are similar to amphetamines, except for the extra methyl group can be detected in blood for 1 to 3 days, in urine for 3 to 5 days, and in hair, up to 90 days. It is not detected in saliva and sweat.

* Barbiturates can be detected in urine for up to 21 days. With other tests, it remains unknown.

* Cannabis is detected 2-3 days after a single use, but up to 2 weeks for habitual use. It is seen in saliva for up to 24 hours, in urine for 2-3 days following a single dose, but up to 12 weeks following habitual use. It is seen up to 90 days in hair follicles.

* Cocaine can be found in saliva for 24 hours, 4-5 days in urine, and up to 90 days in hair follicles.

* Morphine and its derivatives, including hydrocodone is found up to 36 hours in saliva, 2-4 days in urine, and up to 90 days in hair follicles.

* Heroin is seen only in urine for 2 to 4 days.

* PCP can be detected within 3 days in blood and saliva, 3 to 7 days in urine, and up to 90 days in hair follicles.

* Benzodiazepines, such as Valium, can be detected in the urine for up to 42 days.

* Opiates may remain in urine for up to 48 hours.

* Opiate derivatives, such as hydrocodone, may also remain for up to 48 hours in the blood.

As you can see, medications have different time periods when it can be detected in various substances. Therefore, when undergoing drug tests and you are taking a medication that may interfere with your results, always present a prescription by your doctor on a certain medication since not telling them may lead you to lose your employment if they find out the presence of these drugs in your body.

[QVC1212]

What source did you use for these? I'd read in a Journal on psychotropic drugs that benzos was 7-10 days, cocaine was 48-72 hours, amphetamine 48-72 hours, and opiates were 4-5 days. And alcohol is gone the most quickly of them all, much sooner than 12-24 hours. not sure about the rest.

And marijuana can be detected for up to a month after a single, non-habitual use because it resides in fat cells and is fat-soluble, and therefore is not metabolized as quickly. That I know for a fact.

[kingpin]

From my experience, these are mainly guidelines to estimate how long a certain substance could remain in your system. Personally, Ive had Valium stay in my system in excess of 25 days after the last dose. I believe that an individuals metabolism, diet, and level of exercise play the largest role in ridding the body of chemicals.

[QVC1212]

25 days? That's scary. I'd hate to think an ativan I took 3 weeks ago has broken down and is still circulating around . . .

[kingpin]

Ativan has the shortest half-life. I was told by a doctor that if you took one Ativan, most generally you would piss it out the next morning. Now Valium is another story, and the instance I was speaking of, I took entirely too many Valium. Its a miracle I was awake when they kicked in. That was back when I was young and abused meds heavily.

[QVC1212]

It is amazing what the body can endure, especially insofar as it pertains to benzodiazepines. I read one case report in Medscape which reported IV administration of lorazepam (ativan) at 65mg, 300mg and 300mg on days 1, 2 and 3 respectively, during a hospital stay for renal insufficiency secondary to chronic cocaine abuse (http://www.medscape.com/viewarticle/409789) 300mg is a little bit above the recommended maximum dose but apparently the doctors found it necessary for sedation on a ventilator. That wasn't even the problem! The problem was an overdose of propylene glycol, which was 40 times over the daily dose, and PG is the carrier "vehicle" for the ativan. I thought that was interesting anyway. Personally, I have taken too many ativan at one time, but compared to those mega-doses for the hospital pt, the abuse is insignificant by comparison. Not to downplay the dangers of abusing Rx of course.

[mlo]

In short its about the solubility of the drug. Is it water or fat soluble? Which do you think stays in the system longer? Yep, fat-soluble drugs. Ladypam lays it all out brilliantly

I will say that the presence or absence of food is kind of iffy. I read a lot of clinical trials on the drugs I take and most say that when given with food bioavailability and absorption is really not affected. Of course, this is not true with all drugs. If you are interested read the clinical trials. Purdue has found in a clinical trial that when administering 160mg of OxyContin with a high fat meal that it actually increases peak plasma concentration of oxycodone. I have also heard this to be true with hydrocodone but have read no formal documents.

This is take from Purdue Pharmas prescribing information PDF which can be found on their website under OxyContin.

Food Effects

Food has no significant effect on the extent of absorption of oxycodone from OxyContin. However, the peak plasma concentration of oxycodone increased by 25% when a OxyContin 160 mg Tablet was administered with a high-fat meal.

[K-19]

What about Opiates and phencyclidine? Do they stay in your system for like days or weeks or months?

[makaveli25]

Suboxone and methadone are two that come to mind when talking about long half lives. Methadone withdraw was the worst thing I have ever personally been through. The horrible physical symptoms lasted 2-3 weeks. It took months before I mentally felt better. I was only taking 20mg to.

[Dbrent]

very good post but VERY misleading. For example, ive had heroin in my urine for up to 13 days. Yes, 13. But then again i was using grams at a time, and thats probably abnormal. But saying that 2-4 days is misleading.

But in general, certain drugs DO metabolize alot quicker, Marijuana being a obvious example of a drug that gets caught in your fat lipid cells and stays there for a long time.