grammaticalitypunctuation
Whenever I see a sentence starting with "especially," I always get the impression that this is not grammatically correct. From example:
The high water-salt ratio will not be good for you. Especially if you are dehydrated.
I feel like the two sentences should be united with punctuation, not divided.
Am I mistaken?
The expressions different from and different to are perfectly acceptable in the right place. (Brits would not normally use different than.)
But I don't think different from sounds appropriate (or is used correctly) in your example sentence. The second sentence certainly sounds much better.
First (and I should make clear I'm speaking as a Brit!), I don't think we would normally start a sentence with Different from. It's difficult to explain why, but it just doesn't sound right!
Secondly. I think your context would require differently from because it's the method of administration of the drug that is being compared, and in the sentence you quote can be administered is a verb. Effectively, you are saying Drug B can also be administered orally, whereas Drug A cannot (be administered orally). Even so, I still would not start the sentence with different(ly) from.
Similar to me, he is tall. sounds just as wrong to me as does the original Different from phrase. Unfortunately, again, I find it difficult to explain why. (But in this instance, I don't think I would use the word similar in any event.)
I think it is probably because the comparison actually relates to the height (of the person), which is a characteristic of the subject, whereas the juxtaposition of the adjectival phase and the subject itself suggests otherwise. These would be OK:
As I suggested in relation to different from, if you were to retain the current sentence structure, I think Similarly to me ... would be marginally better, but still wouldn't sound 'right'!
Since writing the above, I've consulted a couple of grammar books. These seem to confirm that, in both instances, you need an adverbial phrase - not an adjectival phrase. I think the basic problem with your sentence construction is the presence of (what should be) an adverbial phase adjacent to the subject.
Being angry and tearful, Susan walked out is fine because the adverbial phrase relates to Susan herself.
But even Being different from Drug A, Drug B can also be administered orally. does not sound correct. The fact that it's (just) different from Drug A does not, of itself, mean Drug B can be administered orally. The drugs could differ in other ways without affecting their methods of administration. The issue is not that the drugs themselves are different, but that their methods of administration are (or can be) different.
On the other hand, something like Being available in liquid form, Drug B can also be administered orally. would be fine. In this case, the adverbial phrase is directly related to Drug B and its form.
That may be why Unlike Drug A, Drug B can also be administered orally. is also quite acceptable, because in that sentence the comparison is directly related to their methods of administration - it's not just saying that they are different drugs.
Difference and similarity both concern comparisons between two things - or, more correctly, particular properties/characteristics of two things, and therefore the words different(ly) from and similar(ly) to need to relate to the properties/characteristics of those 'things' and not just to the subject of the sentence (the 'thing' itself).
I don't know whether there is a grammatical reason as such, or whether "that's just the way it is". But, as I'm sure you know, the English language cannot always be determined by strict rules. Sometimes the only answer is that that's the way it has evolved!!
I hope this gives you a bit more understanding - but, as I say, there are not always easy or straight-forward answers to questions regarding the English language.
I think that you may be asking the wrong question. Unless your job is to punctuate someone else's writing without changing any of the words, your main responsibility to readers is to say what you mean coherently and accurately—not merely to say it in a way that you can justify on the basis of some theory of punctuation.
Commas are extremely flexible punctuation marks and can be useful for everything from demarcating major divisions between clauses to indicating parallel words (or word groups) to signaling a natural pause in speech. But overloading a sentence with commas negates their value as signals. Instead of helping readers follow the structure and flow of the sentence, the comma glut obscures the relationship of the various words and word groups to one another. Readers then have to stop and try to reconnect the disjointed pieces of the sentence. Or they stop reading.
As an experiment, I reworked your example twice—once retaining all of the original words but repunctuating the excerpt in an effort to make it read as coherently as possible, and once treating both the wording and the punctuation as subject to alteration. Here are the results.
Changes in punctuation only:
I think sometimes that my use of commas and, occasionally, exclamation marks can be excessive. Whenever I add a word or expression not necessary to the sentence, just like I did with the "not necessary" and like I am doing right now, I always include these words—well, maybe not "always"; "usually" include these inserts—between commas. So, basically, I enjoy writing long sentences joined with lots of commas and (frequently) semicolons and (often) colons—and have been rather prone to using brackets, as well.
When writing lengthy, detailed sentences, I find sometimes I can get carried—or at least I think I do—and can join two, three, or sometimes more usually related but separate ideas that could be separated into individual, perhaps less interesting, sentences.
This version of your original writing still suffers from a couple of lapses into incoherence that no amount of fiddling with punctuation can solve, which leads us to the second revision.
Changes in punctuation and wording:
Sometimes, I think, my use of commas and exclamation marks is excessive. Whenever I add a word or expression that is not necessary to the sentence, as I might have done with "not necessary" and as I am doing right now with this longwinded aside, I always (or usually) set off the words with commas. Basically, I enjoy writing long sentences and punctuating them with lots of commas, as well as with somewhat smaller helpings of semicolons and colons. I have been rather prone to using brackets, too.
When writing lengthy, detailed sentences, I sometimes get carried away and find myself joining two, three, or even more related ideas that could be separated into individual (though, perhaps, less interesting) sentences.
As the second reworking suggests, many of the commas in your original version were serving not to "join" related phrases, but to accommodate extraneous verbiage. Most writing that aims to communicate effectively with readers, rather than to display one's real or simulated stream of consciousness, resolves itself into coherent parts without intervention in the form of overwhelming punctuation.
Best Answer
It is not acceptable in formal or academic writing. (Typically.)
There are exceptions. @oosterwal, @tcovo, and @wooble give good examples of perfectly valid constructions starting with especially (or in wooble's case, starting with because).
An example with because :
An example with especially:
Another :
It's probably acceptable in email correspondence at work, but you have to be aware of the informal tone it gives.
Sometimes deliberate informality can be a good thing, as it gives or creates the sense of or the illusion of a closer relationship. It is more casual as well as being more informal, and this relaxation of 'formal' rules can give the correspondence the same relaxed feel.
'But wait,' I hear you saying, 'aren't you just deliberately and strategically making a mistake if you use it like that? '
"Especially if you use it like that?" I ask.
'No,' you say, 'you're just mocking me. I mean that it isn't just an ugly cousin of the correct sentence structure, which you can choose to use as you please. It's actually broken. It's a solecism."
"Absolutely not," I insist. "Definitely not." I shake my virtual head. "The machinery of language is far more flexible than you think. The rules are beaten into your noggin so that you know how sentences function. One you know these rules and how they operate, the actual syntactic and semantic mechanisms you use to communicate your thoughts can twist, bend, and stretch to fit the shape of current circumstance."
Among friends, it's fine, as long as one of you isn't a grammar absolutist.
It's certainly an acceptable formation in fiction writing, as it mirrors the actual practice that occurs in spoken English.