Cownie asked
Hi, so I have had general anxiety my whole life and panic for the last six years. I've been on Fluoxetine 20mg for the past five years and it seems to be helping. I still have ups and downs like usual. This past year has been a difficult one and i've had a lot more panic attacks lately. I want to travel again but i'm scared to! My Doctor has perscribed me 40mg of fluoxetine. I'm really scared to take it. I don't remember having any side effects from it but do you think I will get side effects when I start the 40mg? I'm just worried it will make my anxiety increase or something.
Answer
Many people that are seemingly stable on a certain medication for several years may go through a rough patch in their life requiring reassessment of the therapy being used. This is a common practice especially among mental health medications. I’m glad you sought help from your doctor instead of ignoring it or shrugging it off, hoping it will pass with time.
Fluoxetine is the generic for Prozac which is what’s known as a selective serotonin reuptake inhibitor, or SSRI, for short. Fluoxetine was the first SSRI approved in the United States in 1987, generally meaning that there is a lot of documented research on this drug available. If you have been taking fluoxetine 20mg for five years continuously and are now increasing your dose to 40mg, mostly likely you will experience very mild side effects, if any at all.
Most side effects occur when a medication is started for the first time. While additional side effects can certainly happen with a dose increase, your body has had quite some time to adjust to the medication so it would be relatively unlikely to have major problems.
If side effects do occur, the following are some possibilities. SSRI's are well known to cause GI-related (gastrointestinal) problems including nausea, diarrhea, loss of appetite, dry mouth, heartburn-like symptoms, constipation, gassiness, vomiting and/or weight loss. These side effects are listed in the order they are most likely to occur. For example, the likelihood that you would experience nausea (the first possible side effect listed) is anywhere from 12% to 29% while weight loss (the least likely) is about 2%. All of these side effects are typically temporary and would most likely subside after a few weeks following your dosage change.
The psychiatric side effects include trouble sleeping, anxiety, nervousness, sleepiness, tremor, abnormal dreams, headache and/or dizziness. It looks like you may be most concerned with the dose increase causing anxiety and the likelihood of this happening is about 6% to 15% according to Clinical Pharmacology, a pharmaceutical reference. So technically, your anxiety could increase by taking a new dose of medication that is prescribed to reduce these very symptoms. You may want to go over the risks versus benefits with your doctor if you are still unsure if you want to start the new dose. The rewards you receive from being controlled on a well-documented medication like fluoxetine might outweigh the chance of experiencing these adverse effects.
Lastly, it is not uncommon for a dose change to take some time to become effective. When first starting on an SSRI, it can take anywhere from 4-12 weeks to effective. A dose increase can similarly have a lag in effectiveness.
