Candy - As Larry said, there is no problem to take higher doses of Effexor XR (venlafaxine) if there are no side effects issues. I'd just like to add a little information on this particular medication.

Effexor differs from other commonly used antidepressants that collectively go by the Name SSRIs (selective serotonin reuptake inhibitors). Examples of SSRIs are: Prozac (fluoxetine), Zoloft (sertraline), Paxil (paroxetine), Celexa (citalopram), Lexapro (escitalopram), and Luvox (fluvoxamine). SSRIs act by blocking the reuptake of the neurotransmitter serotonin between certain specific nerve cells in the brain that are involved in emotion. Serotonin has been shown to be deficient in many people who exhibit depressive &/or anxiety states. There are several other neurotransmitters that interact closely with serotonin and are linked to emotion; specifically norepinephrine (aka noradrenaline) and dopamine. All the neurotransmitters are functionally linked to one another, so that any change in concentration of one has an impact on the functioning of all the others.

At lower doses (< 150mg / day) Effexor act exactly like the SSRIs, but as the dose increases above 150mg / day the concentration of norepinephrine is increased, increasing the activity of nerve cells that use norepinephrine to carry an electrial signal from one nerve cell to another. As you increase the dose of Effexor above 300mg / day there is a significant increase in the concentration of dopamine, by blocking it's reuptake into the nerve cells that use it as a signaling agent increasing their activity (in much the same way as the increase in actvity of serotonin and norepinephrine).

After a certain dosage the activity of SSRIs "plateau"; that is, the reuptake mechanism becomes fully saturated and increasing the dose does not increase the amount of serotonin available, thus an increase in dose no longer results in an increase in antidepressant/antianxiety activity. Effexor activity, on the other hand, does not plateau, because as serotonin activity peaks, significant norepinephrine activity, and subsequently as norepinephrine activity peaks, dopamine neurotransmission increases. Since dopamine and norepinephrine are functionally linked to serotonin, in many cases (but not all) the increase in the neurotransmission of norepinephrine and dopamine result in greater antidepressant/antianxiety activity.

Thus, by increasing your Effexor dose your doctor is quite likely increasing the overall neuronal signaling in your brain, hopefully with the desired results.

BTW, I have seen doses of Effexor XR of 600mg / day used in a couple of cases treatment-resistant depression. I myself was taking 450mg / day for about six months (along with 300mg of Wellbutrin SR - bupropion) when my depression was at it's worst. It worked for me.

I hope that this is of some help - Cam