Medications For Combat PTSD

cont. from

2. Tolerance and withdrawal

   I will use alcohol as the example, because most people have considerable knowledge about it. They just haven't realized that they can transfer this knowledge to other drugs. Pharmacologic tolerance is a critically important subject.

   Consider a very heavy drinker, who drinks every day and more or less all day. Most of the time he is not drunk, in the sense of staggering or slurring or not thinking clearly. He may function quite well at his job with a blood alcohol level that would put a non-drinker almost in a coma. This is because the drinker has developed a tolerance to alcohol. His brain has adjusted to alcohol's presence and slowly adapted its machinery to get everything back to normal. This adjustment is called pharmacologic tolerance, and it takes a while to happen. The brain has developed a steady, compensating excitation to balance the steady sedating effect of chronic alcohol. When the two are exactly in balance, the drinker thinks and behaves more-or-less normally. If the alcohol is suddenly removed, the brain becomes dangerously over-excited, resulting in delirium tremens, DTs. The compensating excitation corrects itself much more slowly than the alcohol leaves the body. This whole set of events is called a withdrawal syndrome.

   The same kind of DT-like withdrawal syndrome of dangerous over-excitement (seizures, hallucinations, etc.) happens after sudden withdrawal from high doses of other sedating drugs that people get tolerant to, such as barbiturates, benzodiazepines (such as Valium), etc. A good rule of thumb is that a patient who has become tolerant to a given drug effect will get a withdrawal syndrome if he or she stops it suddenly. Often, the withdrawal syndrome is the "mirror image" of the original effects of the drug.

   Not all of the effects of a drug are detectable by the person taking it, so tolerance to these changes may not be subjectively felt, either. However, during cold-turkey withdrawal from the drug, a withdrawal syndrome may develop that is the mirror image of effects that the person was never aware of. An example of this is caffeine withdrawal headaches. Most people are unaware of the blood-vessel-narrowing effect of caffeine, but once tolerant to this effect, abrupt discontinuation of caffeine can cause headaches due to blood-vessel dilation.

   The greatest tolerance and the most severe withdrawal reactions happen with long-term use. However, with some drugs, there can be a miniature version of the whole picture with a single dose. Again, alcohol gives a good example: A man who knocks many drinks back one after another and then stops is much more drunk when his blood alcohol level passes a given point on the way up, than later when his blood alcohol level passes the same point on the way down. This is called acute tolerance, because his body has already adjusted to the presence of the alcohol in the few hours since he started drinking. The next morning, during the hangover, he has a mini-withdrawal syndrome making his nervous system overly sensitive -- how loud every sound seems! -- is the mirror image of how much alcohol deadened sound when he was drunk.

   An analogy: You are running a motor boat on a certain compass heading, say due north, on a windless day (no alcohol). Now a cross-wind begins to pick up (gradually increasing steady drinking) and you gradually adjust the rudder to keep on the same heading. Now you are still heading due north, despite the heavy cross-wind. Suppose the wind suddenly dies (suddenly stopping drinking, cold-turkey) and you keep the rudder where it was -- you start going in circles (withdrawal syndrome).

   How much tolerance develops to each drug effect varies a lot from effect to effect and from person to person. A person may develop rapid tolerance to a nasty side-effect, such as dizziness. This means the dizziness actually goes away, not that the patient just gets used to it. So this person can bear with the drug and wait around for the therapeutic effect to kick in. Another person may never get tolerant to the dizziness side-effect and cannot make use of that particular drug. There's no iron-clad way to predict a given person's sensitivity to each of the effects of a given drug or how fast, if at all, he will become tolerant to each effect.

continue: Good Drugs For Combat PTSD

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Reviewed: 04/2006