Re: Contents of the lethal injection

Three drugs, each with a distinct and main purpose.

After positioning the convicted individual on the gurney/bed, a doctor or 
nurse sets up iv (intravenous) line.  This is the route of administration 
for the drugs, and provides direct access to the circulatory system.  When 
a drug is injected iv, it travels with the venous blood through the veins 
directly to the heart and lungs.  From here the blood is pumped throughout 
the body.  It is a very fast way of delivering drugs - drugs injected iv 
will reach the brain in approximately 10 seconds.  

Here are the drugs and their purposes, in sequence:

First, a barbiturate is administered to anesthetize the person (make them 
unconscious).  Barbiturates were originally (and still remain) used for 
surgery.  There are a couple of specific drugs that are probably the 'drug 
of choice': thiopental (sold as Pentothal) is easily dissolved in sterile 
water, as is methohexital (Brevital sodium).   Following the iv 
administration of the barbiturate, the person loses consciousness in about 
10-20 seconds.  Under other circumstances, the anesthesia would probably 
last 20-40 minutes.  It should be noted that barbiturates in general are 
often poor analgesics (pain relieving).  Thus, although the individual may 
lose consciousness, pain perception may be unaffected.  Typically in 
surgical procedures, at least two drugs are administered - an anesthetic 
and an analgesic (or one drug that can produce both).

Second, a neuromuscular blocking agent is administered to paralyze the 
person.  Often the drug administered is similar to curare.  Curare has a 
long and colorful history.  It was used by various South American cultures 
(around the Amazon and Orinoco Rivers) as a poison for arrow tips that were 
used to hunt and kill animals for food.  Hunted animals died from paralysis 
of the skeletal muscles which are used throughout the body, but perhaps 
most importantly in breathing.  Use of curare derivative in executions 
results in a rapid paralysis of most major muscle groups.  Initially, 
effects are observed in small rapidly moving muscles (eyes, fingers) 
followed by larger ones.  Eventually, the diaphragm is paralyzed, resulting 
in cessation of breathing.

Finally, a lethal dose of potassium chloride is injected.  Potassium is the 
main positively charged ion inside of all of our cells that is essential 
for our day-to-day living.  Banana's are a very good source of potassium.  
However, like many things, too much of a good thing can be bad for you.  If 
you consult a biology or physiology textbook you can learn about how 
important it is to maintain a balance in ions.  The lethal dose of 
potassium chloride produces hyperkalemia (too much potassium; you ask why 
the word 'kalemia'? -- potassium's chemical symbol is K).  One of the main 
effects of hyperkalemia is a change in the electrical activity of the 
heart.  The lethal dose administered basically stops the heart.

So, in summary, the drugs used knock them out, stop the breathing, and then 
stop the heart.  Death.

For additional information on:
 the processes involved, the specific drugs, or about lethal injections

Consider consulting:

a. Physiology or cardiology textbooks
b. Pharmacology textbooks (Goodman and Gilman's The Pharmacological Basis 
         of Therapeutics is the best out there)
c. Amnesty International (http://www.amnesty.org/) has lots of information, 
         albeit from a biased perspective

Hope this helps you out.