In terms of molecular structure, synephrine has a phenethylamine skeleton, with a phenolic hydroxy - group, an alcoholic hydroxy- group, and an N -methylated amino -group. Alternatively, synephrine might be described as a phenylethanolamine with an N -methyl and p -hydroxy substituent. The amino-group confers basic properties on the molecule, whereas the phenolic –OH group is weakly acidic: the apparent (see original article for discussion) pK a s for protonated synephrine are (phenolic H) and (ammonium H). 
It seems quite clear that the medical community is blind to the lies that go on and simply take these adverse effect reports according to a 2004 WebMD study of patients, 22% lied about smoking, 16% lied about how much or how often they drink alcohol and 12% lied about recreational drug use. With this taken into consideration, it would appear that synephrine is a very safe supplement considering that it is estimated that over 100 million synephrine containing supplements have been sold, which makes these reports absurd considering that 12 million of the people using synephrine could have also been at risk due to illegal drug use which seems to go unreported to the medical community. Additionally, doctors rarely do a full medical background check before they publish these articles, instead treating each incident independent of the patients medical history.
The Bitter Orange itself (the parent plant) has been linked to increased systolic and diastolic blood pressure.  While a common patented blend of P-synephrine known as Xenadrine EFX (containing just mg synephrine) has been linked to an increase in blood pressure, another patented blend, Advantra-Z (which contains a significantly higher dose of synephrine at mg along with active bioflavonoids such as naringen and hesperidin ) has not. Both appear to increase heart rate from baseline though ( BPM and BPM, respectively).