Posted by ed_uk on August 15, 2005, at 5:51:25
How do you explain these results? - SSRI vs SSRI
Ann Clin Psychiatry. 2005 Apr-Jun;17(2):65-9.
A double-blind comparison of escitalopram and paroxetine in the long-term treatment of generalized anxiety disorder.
Bielski RJ, Bose A, Chang CC.
Summit Research Network, 4084 Okemos Road. Suite C, Okemos, MI 48864, USA. rbielski@summitnetwork.com
BACKGROUND: This study compared the efficacy and tolerability of escitalopram, a newer SSRI, with paroxetine in the treatment of generalized anxiety disorder (GAD). METHODS: Patients with DSM-IV-defined GAD were randomized to receive 24 weeks of double-blind flexible-dose treatment with either escitalopram (10-20 mg/day) or paroxetine (20-50 mg/day), followed by a 2-week, double-blind, down-titration period. Mean change from baseline to endpoint (LOCF) in Hamilton Anxiety Scale (HAMA) scores was the primary efficacy variable. RESULTS: Mean baseline HAMA scores for the escitalopram (N = 60) and paroxetine (N = 61) groups were 23.7 and 23.4, respectively. After 24 weeks of treatment, mean changes in HAMA scores were -15.3 and -13.3 for escitalopram and paroxetine, respectively (p = 0.13 - not significant). Significantly fewer patients withdrew from escitalopram than paroxetine treatment due to adverse events (6.6% vs. 22.6%; p = 0.02). The frequency of treatment-emergent adverse events was higher with paroxetine vs. escitalopram: overall (88.7% vs. 77.0%), insomnia (25.8% vs. 14.8%), constipation (14.5% vs. 1.6%), ejaculation disorder (30.0% vs. 14.8%), anorgasmia (26.2% vs. 5.9%), and decreased libido (22.6% vs. 4.9%). Conversely, diarrhea and upper respiratory tract infection were reported more with escitalopram than paroxetine (21.3% vs. 8.1%, and 14.8% vs. 4.8%, respectively). CONCLUSIONS: These results support the use of escitalopram as a first-line treatment for GAD.
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Here is my explanation....... (just a guess)........
1. Paroxetine doses >20mg/day have not been shown to be more effective than 20mg for GAD. Study patients received up to 50mg.
2. Many people who take escitalopram for anxiety appear to require doses up to ~40mg/day. Study patients recived a maximum of 20mg. In the short term, 40mg escitalopram is probably no more effective than 20mg. Some people may respond better to ~40mg in the long term?
3. Paroxetine caused more side effects due to the relatively high doses prescribed. Escitalopram was better tolerated because the doses prescribed were relatively low.
4. Diarrhea was more common with escitalopram because paroxetine is (very) weakly anticholinergic. Anticholinergics are constipating. Hmm, I'm not convinced about this one, paroxetine is only very weakly anticholinergic.
Second explanation........
I'm wrong about escitalopram. It really is better tolerated than paroxetine.
Yeah I know, escitalopram is a more selective SSRI than paroxetine....... but paroxetine's pretty selective too ya know? I'm not convinced that it effects NE reuptake enough to be relevent, especially at low doses.
~Ed
PS. Grrr. This was supposed to be a flexible dose study..... but the doses prescribed were limited by fixed ranges. Hmmmm.
PPS. Am I too cynical?
poster:ed_uk
thread:541835
URL: http://www.dr-bob.org/babble/20050811/msgs/541835.html