Here is a benzodiazepine comparison chart. It shows the half-lives and dosage conversion for all of the benzos. the two you were interested in are highlighted.
Alprazolam (Xanax) has a half-life of 6-12 hrs. It's potency is shown at .5mg
The next on your list is Lorazepam
(Ativan). It's half-life is 10-20 hrs and it's equivalent potency is 1mg.
So, Ativan has about a 8 hr longer half life. Meaning the peak plasma levels will go up slower but will be maintained for a longer period of time.
Xanax, is probably the #1 prescribed benzo. for panic attacks. Because it has a shorter half-life. So peak plasma levels are going to be reached and felt more quickly, and than it's levels drop quickly. Xanax is twice as potent at a two to one ratio.
Now, as far as why some are used more for SA or anxiety disorder in general. While some are used for acute panic attacks. Well, it all comes down to the half-life of each med. The longer acting benzos., but no less stronger or weaker than another benzodiazepine. To say that is a misnomer. Some ,like clonazepam have a long half-life of 45-48hrs and so it suits the needs of SA and GAD anxiety types more. Another, is diazepam, which even though it may take 2- 10mg tabs to equal the one 1mg tab of clonazepam. Does that make it a weaker drug. maybe on surface value, but realize this. that the Valium half-life is a whopping 100+hrs. So, to say that you can take 2mg of this "stronger"'med which lasts for 4hrs or you can take 20mg of a slower, but still potent benzo with a 100 hr half-life is not relevant. You can see their strengths and weaknesses for what they are( slow acting or fast acting). One last thing about the longer acting benzos. they are often used, as is the case of diazepam, to come of the addiction or tolerance built to a quicker acting Xanax or Ativan or Tamezapam. This is simply for the fact that if you want to titrate down using another longer acting benzo. as a buffer. than diazepam is #1 for this because of it's long half-life. The longer the plasma levels stay up in your body and slowly decline. the easier the taper going to be. Thats why in extreme , high dosage tolerance many will use the taper method with valium because it sticks around and once rid of the original faster acting benzo. The reduction of diazepam goes rather smoothly.
So, finally the two mentioned. first off with all of my years either listening to others tell it or from first hand benzo. experience with Klonopin, Valium, Xanax, and Ativan. If you were to separate the longer acting, (30+hrs) and the shorter acting, (4-25)hrs. into the two distinguishable groups. You will have one person whose physiological nad psychological make-up will say Xanax saves me from panic attacks. while you will have others that prefer Ativan. It's the same with the long- acting benzos. I really get tired on valium. I know others that prefer Valium and it's longer half-life over Klonopin, which does not make me tired. This isn't even factoring in many benzos. on that list. Just the ones that are more prescribed
Here are some links on the two and comparisons:
http://www.drugs.com/forum/featured-...nax-53408.html
http://www.healthboards.com/boards/anxiety/356263-xanax-vs-klonopin-vs-ativan.html
http://www.differencebetween.info/difference-between-xanax-and-ativan
http://www.askapatient.com/comparedrugs.asp?class=ANTIANXIETY
http://www.askapatient.com/viewrating.asp?drug=17794&name=ATIVAN
http://www.askapatient.com/viewrating.asp?drug=18276&name=XANAX
http://en.wikipedia.org/wiki/List_of_benzodiazepines
http://web4health.info/en/answers/bi...o-overview.htm
BENZODIAZEPINE EQUIVALENCE TABLE
(Benzodiazepine Equivalency Table)
Revised April 2007
This Benzodiazepine Equivalence Table is based on the extensive research and clinical experience of Professor C Heather Ashton, DM, FRCP, Emeritus Professor of Clinical Psychopharmacology at the University of Newcastle upon Tyne, England. Sources: NRHA Drug Newsletter, April 1985 and Benzodiazepines: How they Work & How to Withdraw (The Ashton Manual), 2002. The approximate equivalent doses to 10mg diazepam (Valium) are given.
For a discussion of half-lives and equivalencies see also the Benzo FAQ document.
Benzodiazepines1 |
Half-life (hrs)2
[active metabolite] |
Approximately Equivalent
Oral dosages (mg)3 |
Market Aim4 |
Alprazolam
(Xanax, Xanor, Tafil) |
6-12 |
0.5 |
a |
Bromazepam
(Lexotan, Lexomil) |
10-20 |
5-6 |
a |
Chlordiazepoxide
(Librium) |
5-30 [36-200] |
25 |
a |
Clobazam
(Frisium)5 |
12-60 |
20 |
a,e |
Clonazepam
(Klonopin, Rivotril)5 |
18-50 |
0.5 |
a,e |
Clorazepate
(Tranxene) |
[36-200] |
15 |
a |
Diazepam
(Valium) |
20-100 [36-200] |
10 |
a |
Estazolam
(ProSom, Nuctalon) |
10-24 |
1-2 |
h |
Flunitrazepam
(Rohypnol) |
18-26 [36-200] |
1 |
h |
Flurazepam
(Dalmane) |
[40-250] |
15-30 |
h |
Halazepam
(Paxipam) |
[30-100] |
20 |
a |
Ketazolam
(Anxon) |
30-100 [36-200] |
15-30 |
a |
Loprazolam
(Dormonoct) |
6-12 |
1-2 |
h |
Lorazepam
(Ativan, Temesta, Tavor) |
10-20 |
1 |
a |
Lormetazepam
(Noctamid) |
10-12 |
1-2 |
h |
Medazepam
(Nobrium) |
36-200 |
10 |
a |
Nitrazepam
(Mogadon) |
15-38 |
10 |
h |
Nordazepam
(Nordaz, Calmday) |
36-200 |
10 |
a |
Oxazepam
(Serax, Serenid,
Serepax, Seresta) |
4-15 |
20 |
a |
Prazepam
(Centrax, Lysanxia) |
[36-200] |
10-20 |
a |
Quazepam (Doral) |
25-100 |
20 |
h |
Temazepam
(Restoril, Normison,
Euhypnos) |
8-22 |
20 |
h |
Triazolam
(Halcion) |
2 |
0.5 |
h |
Non-benzodiazepines
with similar effects 1, 6 |
|
|
|
Zaleplon
(Sonata) |
2 |
20 |
h |
Zolpidem
(Ambien, Stilnoct, Stilnox) |
2 |
20 |
h |
Zopiclone
(Zimovane, Imovane) |
5-6 |
15 |
h |
Eszopiclone
(Lunesta) |
6
(9 in elderly) |
3 |
h |