Low blood pressure (i.e. hypotension) is not a common side effect of Lexapro (escitalopram).
The prescribing information for Lexapro does not list it as occurring during clinical trials but it has been reported during the post-marketing experience.
Postmarketing reports are voluntary reports of side effects and/or other drug concerns. The FDA describes it as follows:
Because all possible side effects of a drug can't be anticipated based on preapproval studies involving only several hundred to several thousand patients, FDA maintains a system of postmarketing surveillance and risk assessment programs to identify adverse events that did not appear during the drug approval process.
It is always difficult to discern how common or serious reported postmarketing side effects are because they are reported voluntarily from an indeterminant population size and may not even be linked to exposure to the drug in question.
Therefore, even though low blood pressure has been reported for Lexapro, it isn't definitively known whether or not it truly was the cause in reported instances.
The 'Guidelines for the Treatment of Major Depressive Disorder', which goes over antidepressant therapy in great detail, does not associate low blood pressure with SSRI (selective serotonin reuptake inhibitor) drugs, a class which includes Lexapro.
Having said all of the above, the prescribing information for Lexapro does list hypotension (i.e. low blood pressure) as a possible symptom of overdose:
Symptoms most often accompanying escitalopram overdose, alone or in combination with other drugs and/or alcohol, included convulsions, coma, dizziness, hypotension, insomnia, nausea, vomiting, sinus tachycardia, somnolence, and ECG changes (including QT prolongation and very rare cases of torsade de pointes).
There certainly is a chance that some individuals may be more susceptible to experiencing low blood pressure on Lexapro, but based on available data for the drug, it does seem to be quite rare.
The blood pressure you state in your question (105/48) is low, especially the diastolic number (the second one).
It's unlikely that Lexapro is the culprit, but you shouldn't rule it out if nothing else has changed with your medication regimen. Be sure to discuss your situation with your doctor so you can be appropriately evaluated.
Hypotension (i.e. low blood pressure) isn't a listed side effect of Lexapro based on clinical trial data, but has been reported during postmarketing experience. Overall, the risk of experiencing low blood pressure with Lexapro is low.