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The '''volume of distribution''' (V<sub>D</sub>), also known as '''apparent volume of distribution''', is a [[pharmacology|pharmacological]], theoretical volume that the total amount of administered drug would have to occupy (if it were uniformly distributed), to provide the same concentration as it currently is in blood plasma. Therefore, if VD is greater, it shows that the drug is more diluted than it should be (in the blood plasma), meaning more of it is distributed in tissue (i.e. not in plasma). It is defined as the [[Distribution (pharmacology)|distribution]] of a [[medication]] between [[Blood plasma|plasma]] and the rest of the body after [[oral administration|oral]] or [[parenteral]] dosing. It is defined as the theoretical  volume in which the total amount of drug would need to be uniformly distributed to produce the desired blood concentration of a drug.<ref>http://www.merckmanuals.com/professional/sec21/ch324/ch324d.html</ref><ref name="urlUntitled Document">{{cite web |url=http://cpharm.vetmed.vt.edu/VM8314/VM8314PharmaModeling.htm |title=vetmed.vt.edu |work= |accessdate=}}</ref> In rough terms, drugs with high lipid solubility (non-polar), low rates of ionization or low plasma binding capabilities have higher volumes of distribution than drugs which are more polar, more highly ionized or exhibit high plasma binding in the body's environment.
It is very common to have a dental emergency -- a fractured tooth, an abscess, or severe pain when chewing. Over-the-counter pain medication is just masking the problem. Seeing an emergency dentist is critical to getting the source of the problem diagnosed and corrected as soon as possible.<br><br>Here are some common dental emergencies:<br>Toothache: The most common dental emergency. This generally means a badly decayed tooth. As the pain affects the tooth's nerve, treatment involves gently removing any debris lodged in the cavity being careful not to poke deep as this will cause severe pain if the nerve is touched. Next rinse vigorously with warm water. Then soak a small piece of cotton in oil of cloves and insert it in the cavity. This will give temporary relief until a dentist can be reached.<br><br>At times the pain may have a more obscure location such as decay under an old filling. As this can be only corrected by a dentist there are two things you can do to help the pain. Administer a pain pill (aspirin or some other analgesic) internally or dissolve a tablet in a half glass (4 oz) of warm water holding it in the mouth for several minutes before spitting it out. DO NOT PLACE A WHOLE TABLET OR ANY PART OF IT IN THE TOOTH OR AGAINST THE SOFT GUM TISSUE AS IT WILL RESULT IN A NASTY BURN.<br><br>Swollen Jaw: This may be caused by several conditions the most probable being an abscessed tooth. In any case the treatment should be to reduce pain and swelling. An ice pack held on the outside of the jaw, (ten minutes on and ten minutes off) will take care of both. If this does not control the pain, an analgesic tablet can be given every four hours.<br><br>Other Oral Injuries: Broken teeth, cut lips, bitten tongue or lips if severe means a trip to a dentist as soon as possible. In the mean time rinse the mouth with warm water and place cold compression the face opposite the injury. If there is a lot of bleeding, apply direct pressure to the bleeding area. If bleeding does not stop get patient to the emergency room of a hospital as stitches may be necessary.<br><br>Prolonged Bleeding Following Extraction: Place a gauze pad or better still a moistened tea bag over the socket and have the patient bite down gently on it for 30 to 45 minutes. The tannic acid in the tea seeps into the tissues and often helps stop the bleeding. If bleeding continues after two hours, call the dentist or take patient to the emergency room of the nearest hospital.<br><br>Broken Jaw: If you suspect the patient's jaw is broken, bring the upper and lower teeth together. Put a necktie, handkerchief or towel under the chin, tying it over the head to immobilize the jaw until you can get the patient to a dentist or the emergency room of a hospital.<br><br>Painful Erupting Tooth: In young children teething pain can come from a loose baby tooth or from an erupting permanent tooth. Some relief can be given by crushing a little ice and wrapping it in gauze or a clean piece of cloth and putting it directly on the tooth or gum tissue where it hurts. The numbing effect of the cold, along with an appropriate dose of aspirin, usually provides temporary relief.<br><br>In young adults, an erupting 3rd molar (Wisdom tooth), especially if it is impacted, can cause the jaw to swell and be quite painful. Often the gum around the tooth will show signs of infection. Temporary relief can be had by giving aspirin or some other painkiller and by dissolving an aspirin in half a glass of warm water and holding this solution in the mouth over the sore gum. AGAIN DO NOT PLACE A TABLET DIRECTLY OVER THE GUM OR CHEEK OR USE THE ASPIRIN SOLUTION ANY STRONGER THAN RECOMMENDED TO PREVENT BURNING THE TISSUE. The swelling of the jaw can be reduced by using an ice pack on the outside of the face at intervals of ten minutes on and ten minutes off.<br><br>If you liked this article and you would like to get more info with regards to [http://www.youtube.com/watch?v=90z1mmiwNS8 dentist DC] nicely visit our web site.
 
Volume of distribution may be increased by [[renal failure]] (due to fluid retention) and [[liver failure]] (due to altered body fluid and [[plasma protein binding]]). Conversely it may be decreased in dehydration.
 
The [[initial volume of distribution]] describes blood concentrations prior to attaining the apparent volume of distribution and uses the same formula.
 
==Equations==
The volume of distribution is given by the following equation:
 
:::::::<math>{V_{D}} = \frac{\mathrm{total \ amount \ of \ drug \ in \ the \ body}}{\mathrm{drug \ blood \ plasma \ concentration}}</math>
 
Therefore the dose required to give a certain plasma concentration can be determined if the V<sub>D</sub> for that drug is known. The V<sub>D</sub> is '''not''' a physiologic value; it is more a reflection of how a drug will distribute throughout the body depending on several physicochemical properties, e.g. solubility, charge, size, etc.
 
The units for Volume of Distribution are typically reported in  (ml or liter)/kg body weight.  The fact that V<sub>D</sub> is a ratio of a theoretical volume to a fixed unit of body weight explains why the V<sub>D</sub> for children is typically higher than that for adults, even though children are smaller and weigh less. As body composition changes with age, V<sub>D</sub> decreases.
 
The V<sub>D</sub> may also be used to determine how readily a drug will displace into the body tissue compartments relative to the blood:
 
:::::::<math>{V_{D}} = {V_{P}} + {V_{T}} \left(\frac{fu}{fu_{t}}\right)</math>
 
Where:
 
* V<sub>P</sub> = plasma volume
 
* V<sub>T</sub> = apparent tissue volume
 
* fu = fraction unbound in plasma
 
* fu<sub>T</sub> = fraction unbound in tissue
 
==Examples==
{{main|Table of volume of distribution for drugs}}
If you administer a dose D of a drug intravenously in one go (IV-bolus), you would naturally expect it to have an immediate blood concentration <math>C_0</math> which directly corresponds to the amount of blood contained in the body <math>V_{blood}</math>. Mathematically this would be:
 
<math>C_0 = D/V_{blood}</math>
 
But this is generally not what happens. Instead you observe that the drug has distributed out into some other volume (read organs/tissue). So probably the first question you want to ask is: how much of the drug is no longer in the blood stream?
The volume of distribution <math>V_D</math> quantifies just that by specifying how big a volume you would need in order to observe the blood concentration actually measured.  
 
A practical example for a simple case (mono-compartmental) would be to administer D=8&nbsp;mg/kg to a human. A human has a blood volume of around <math>V_{blood}=</math>0.08 l/kg
.<ref name="alberts_table">{{Cite web|url=http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Search&db=books&doptcmdl=GenBookHL&rid=mboc4.table.4143|title=Leukocyte functions and percentage breakdown|accessdate=2007-04-14|publisher=NCBI Bookshelf|year=2005|author=Alberts, Bruce|work=Molecular Biology of the Cell}}</ref>
This gives a <math>C_0=</math>100&nbsp;µg/ml if the drug stays in the blood stream only, and thus its volume of distribution is the same as <math>V_{blood}</math> that is <math>V_D=</math> 0.08 l/kg. If the drug distributes into all body water the volume of distribution would increase to approximately <math>V_D=</math>0.57 l/kg
<ref name=textbookofmedicalphysiology5thed>{{cite book |title=Textbook of Medical Physiology |last=Guyton |first=Arthur C. |year=1976|edition=5th|publisher=W.B. Saunders|location=Philadelphia|page= 424|isbn=0-7216-4393-0}}</ref>
 
If the drug readily diffuses into the body fat the volume of distribution may increase dramatically, an example is [[chloroquine]] which has a <math>V_D=</math>250-302 l/kg
<ref>{{cite journal |author=Wetsteyn JC |title=The pharmacokinetics of three multiple dose regimens of chloroquine: implications for malaria chemoprophylaxis |journal=Br J Clinical Pharmacology |volume=39 |issue=6 |pages=696–9 |year=1995 |pmid=7654492
|doi= |pmc=1365086}}</ref>
 
In the simple mono-compartmental case the volume of distribution is defined as: <math>V_D=D/C_0</math>, where the <math>C_0</math> in practice is an extrapolated concentration at time=0 from the first early plasma concentrations after an IV-bolus administration (generally taken around 5min - 30min after giving the drug).
 
{| class="wikitable"
| '''Drug''' || '''V<sub>D''' || '''Comments'''
|-
| [[Warfarin]] || 8L  || Reflects a high degree of plasma protein binding.
|-
| [[Theophylline]], [[Ethanol]]|| 30L  || Represents distribution in total body water.
|-
| [[Chloroquine]] || 15000L || Shows highly [[lipophilic]] molecules which sequester into total [[body fat]].
|-
| [[NXY-059]] ||  8L  || Highly-charged [[hydrophilic]] molecule.
|}
 
==Sample values and equations==
 
{{DoseConcentrationClearance}}
 
==References==
{{reflist}}
 
==External links==
* [http://www.nottingham.ac.uk/nmp/sonet/rlos/bioproc/vd/index.html Tutorial on volume of distribution]
* [http://www.icp.org.nz/html/volume_of_distribution.html Overview at icp.org.nz]
* [http://web.vet.cornell.edu/public/pharmacokinetics/pk/avd.html Overview at cornell.edu]
* [http://mips.stanford.edu/public/classes/pharmacokinetics/2006/Lin_comp/VolofDis/VolDist1.html Overview at stanford.edu]
* [http://www.boomer.org/c/p3/c05/c0507.html Overview at boomer.org]
 
{{Pharmacology}}
 
[[Category:Pharmacology]]
[[Category:Pharmacokinetics]]

Latest revision as of 21:24, 25 August 2014

It is very common to have a dental emergency -- a fractured tooth, an abscess, or severe pain when chewing. Over-the-counter pain medication is just masking the problem. Seeing an emergency dentist is critical to getting the source of the problem diagnosed and corrected as soon as possible.

Here are some common dental emergencies:
Toothache: The most common dental emergency. This generally means a badly decayed tooth. As the pain affects the tooth's nerve, treatment involves gently removing any debris lodged in the cavity being careful not to poke deep as this will cause severe pain if the nerve is touched. Next rinse vigorously with warm water. Then soak a small piece of cotton in oil of cloves and insert it in the cavity. This will give temporary relief until a dentist can be reached.

At times the pain may have a more obscure location such as decay under an old filling. As this can be only corrected by a dentist there are two things you can do to help the pain. Administer a pain pill (aspirin or some other analgesic) internally or dissolve a tablet in a half glass (4 oz) of warm water holding it in the mouth for several minutes before spitting it out. DO NOT PLACE A WHOLE TABLET OR ANY PART OF IT IN THE TOOTH OR AGAINST THE SOFT GUM TISSUE AS IT WILL RESULT IN A NASTY BURN.

Swollen Jaw: This may be caused by several conditions the most probable being an abscessed tooth. In any case the treatment should be to reduce pain and swelling. An ice pack held on the outside of the jaw, (ten minutes on and ten minutes off) will take care of both. If this does not control the pain, an analgesic tablet can be given every four hours.

Other Oral Injuries: Broken teeth, cut lips, bitten tongue or lips if severe means a trip to a dentist as soon as possible. In the mean time rinse the mouth with warm water and place cold compression the face opposite the injury. If there is a lot of bleeding, apply direct pressure to the bleeding area. If bleeding does not stop get patient to the emergency room of a hospital as stitches may be necessary.

Prolonged Bleeding Following Extraction: Place a gauze pad or better still a moistened tea bag over the socket and have the patient bite down gently on it for 30 to 45 minutes. The tannic acid in the tea seeps into the tissues and often helps stop the bleeding. If bleeding continues after two hours, call the dentist or take patient to the emergency room of the nearest hospital.

Broken Jaw: If you suspect the patient's jaw is broken, bring the upper and lower teeth together. Put a necktie, handkerchief or towel under the chin, tying it over the head to immobilize the jaw until you can get the patient to a dentist or the emergency room of a hospital.

Painful Erupting Tooth: In young children teething pain can come from a loose baby tooth or from an erupting permanent tooth. Some relief can be given by crushing a little ice and wrapping it in gauze or a clean piece of cloth and putting it directly on the tooth or gum tissue where it hurts. The numbing effect of the cold, along with an appropriate dose of aspirin, usually provides temporary relief.

In young adults, an erupting 3rd molar (Wisdom tooth), especially if it is impacted, can cause the jaw to swell and be quite painful. Often the gum around the tooth will show signs of infection. Temporary relief can be had by giving aspirin or some other painkiller and by dissolving an aspirin in half a glass of warm water and holding this solution in the mouth over the sore gum. AGAIN DO NOT PLACE A TABLET DIRECTLY OVER THE GUM OR CHEEK OR USE THE ASPIRIN SOLUTION ANY STRONGER THAN RECOMMENDED TO PREVENT BURNING THE TISSUE. The swelling of the jaw can be reduced by using an ice pack on the outside of the face at intervals of ten minutes on and ten minutes off.

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