Gemara

(Rabah bar Rav Huna): A Shasuy (one who drank) may not pray. If he did, it was a valid prayer;

A Shikor (one who is drunk) may not pray. If he did, it was an abomination.

(R. Aba or R. Menasiya): A Shasuy is one who can speak [properly] in front of the king [even though he drank]. A Shikor is one who cannot.

Berachos 22b (Rabah): If one prayed and later found excrement, even though he transgressed, his Shemoneh Esreh was valid.

Objection (Rava): "Zevach Resha'im To'evah" - (the Korban of a Rasha, i.e.) his Shemoneh Esreh is an abomination!

Rishonim

Rosh (6:5) and Tosfos (64a DH Shikor): If a Shikor prayed, it was an abomination. He was not Yotzei. He prays again. Similarly, in Berachos we say that if one prayed and later found excrement nearby, since he transgressed, his Tefilah was an abomination, and he must pray again. It is not clear whether Berachos are like Tefilah regarding excrement and Shikor. They are not the same in all ways. L'Chatchilah, a Shasuy may not pray until his wine wears off, but he may bless l'Chatchilah Birkas ha'Mazon and all Berachos. The Yerushalmi says "v'Achalta v'Savata [u'Verachta]" - even if you are Medumdam.

Beis Yosef (OC 185 DH Im): Medumdam is Shasuy.

Tosfos (ibid.): Even if one drank more than a Revi'is of mixed wine, he may not pray. Surely, one need not bless again due to urine. Even if we equate Berachos to Tefilah regarding excrement, urine is not as stringent. The Torah forbids only facing falling urine. Chachamim decreed about Vadai urine, but not about a Safek [to obligate one to check for it before praying].

Poskim

Shulchan Aruch (OC 99:1): If one drank a Revi'is of wine. he may not pray until his wine wears off. If he drank more and prayed, it is valid only if he could speak in front of the king.

Rema: Keri'as Shema is like Tefilah. One may bless other Berachos even if he is Shikur.

Shulchan Aruch (185:4): Even if one is so drunk that he cannot speak properly, he may bless Birkas ha'Mazon.

Shulchan Aruch (5): If one blessed [Birkas ha'Mazon] there was excrement in front of him, or he was Shikor (i.e. totally - Be'er ha'Golah inserted this word into the text), Tosfos and the Rosh were unsure whether he must bless again.

Question (Taz 2): I do not understand the Shulchan Aruch. This is based on Tosfos 64a. Tosfos' Safek about Berachos was only if Medumdam is Shasuy. If it is Shikor, and even so the Berachah was valid, there is no Safek about Shikor, or about excrement. Since Shikor is Kosher (Sa'if 4), even though he cannot speak properly and he is Pasul for Tefilah, even so he is Kosher for Berachos. Why did the Shulchan Aruch immediately after this (in this Sa'if) bring the Safek of Tosfos and the Rosh? The Levush understood that the Safek is only about excrement. This is wrong. Surely, they are the same, like Tosfos says explicitly. Do not say that in Sa'if 4, he can speak in front of the king. Surely, one who cannot speak properly, cannot speak in front of the king! The only distinction we find in Tefilah (99:1) is between Shasuy and Shikor. A Shasuy need not pray again, but a Shikor must pray again. There is no distinction within Shikor. Also, there the Rema explicitly said that the Shikor who is Pasul for Tefilah is Kosher for Berachos. If so, what is the Safek here? With difficulty, we must say that in Sa'if 4, the Mechaber relied on what he wrote here, that Shikur is a Safek. Birkas ha'Mazon is mid'Oraisa, so we are stringent, and obligate him to bless. Other Berachos are mid'Rabanan, so he does not bless when Shikor. Still, it is difficult, for in 99:1, the Rema equated all Berachos regarding the Chiyuv of a Shikor, and here he did not say anything.

Answer (Kaf ha'Chayim 13): The Mechaber rules like Tosfos in Berachos, who rules like the Yerushalmi. In Sa'if 4, he permits a Shikor. Here he brings the Safek of Tosfos in Eruvin, to teach that l'Chatchilah one should avoid the situation.

Mishnah Berurah (5): If one prayed and later found excrement in front of him or within four Amos to the side, in a place where he should have been unsure, and he was negligent and did not check, he must pray again, for Zevach Resha'im To'evah. The same applies to Keri'as Shema. Tosfos and the Rosh were unsure. Perhaps the same applies to Birkas ha'Mazon. Or, perhaps Birkas ha'Mazon is more lenient, for we find that a Shasuy may not pray, but surely he may bless Birkas ha'Mazon.

Mishnah Berurah (6): Totally Shikur means that he cannot speak in front of the king. They are unsure whether he must bless again after the wine wears off if the food was not yet digested. (We do not discuss one who was as drunk as Lot. He is considered a lunatic, and is exempt from all Mitzvos. All would obligate him to bless again.) In Sa'if 4, the Shulchan Aruch permits blessing, i.e. if he can speak in front of the king. Several Acharonim asked that if he cannot speak properly, presumably he cannot speak in front of the king, and even so the Yerushalmi permits! The Acharonim concluded that if he was so drunk, even so he should bless. L'Chatchilah, he must be careful to bless before reaching such a state.

Mishnah Berurah (7): They agree that l'Chatchilah, one may not bless any Berachah or speak Divrei Torah in front of excrement. The Torah forbids this - "v'Hayah Machanecha Kodesh." The verse does not mention Tefilah. Rather, every matter of Kedushah is forbidden in a filthy place. The Safek is only if he already blessed, and afterwards found filth. Olas Tamid and Eliyahu Rabah in the name of the Bach say that when he finds excrement within his four Amos, he must bless again if the food was not yet digested. Also the Ramban says so. The Ramban brought the Safek of Tosfos, and concluded that Tefilah and other Divrei Kedushah are the same.

Bi'ur Halachah (DH Im): See what I wrote in Mishnah Berurah, from the Levush. If he knew from the beginning and transgressed an Isur Torah, surely he must bless again. Here he was Shogeg, and did not know that there is excrement. He sinned through negligence of not checking. Perhaps the Gemara requires praying again only for Tefilah, which is stringent, but not for Birkas ha'Mazon. However, it seems that the Pri Megadim in Siman 76 explains this Sa'if simply. I.e. even if he knew from the beginning, it is a Safek. Tosfos and the Ramban connote that their Safek is about one who found out afterwards. Perhaps the Pri Megadim means that the Mechaber is unsure in every case. Since the Gemara was stringent about Tefilah even if he found it afterwards, the Mechaber discussed this case, but the Safek about Birkas ha'Mazon is in every case. This requires investigation. Chayei Adam holds that he need not bless again even if he knew from the beginning. He holds like the Pri Megadim, that the Safek is in every case, and he is lenient b'Di'eved. This is not called a Safek Torah, for mid'Oraisa, in every case he was Yotzei b'Di'eved. It is a mere fine mid'Rabanan regarding Tefilah. It is lighter than other cases of Mitzvah ha'Ba b'Aveirah. I disagree. This is more stringent, since all know that that all Divrei Kedushah are forbidden in a place of filth (Rambam Hilchos Kri'as Shema 3:4)! "Ki Devar Hash-m Bazah" - how is he Yotzei after disgracing Hash-m's word?! What was Chayei Adam's question? Tosfos proved that Birkas ha'Mazon is more lenient than Tefilah, since we are lenient for a Shikor. We are not lenient about Keri'as Shema at all (Rema 99:1). The Gra's text of the Yerushalmi forbids a Shikor to say Shma. The Rambam holds that one who found excrement must repeat Birkas ha'Mazon. Surely, if one knew from the beginning and transgressed b'Mezid, we should obligate him to repeat it, for the Ramban and several Acharonim are stringent about Tosfos' Safek.

Kaf ha'Chayim (14): One repeats only Tefilah or Keri'as Shema, but not Birkas ha'Mazon or other Berachos. If possible, he should eat more and bless with intent also for what he ate before, or hear Birkas ha'Mazon from someone else. If not, he thinks it in his heart.

Shulchan Aruch (ibid.): Surely, one need not bless again due to urine.

Mishnah Berurah (8): This is when he blessed, and then found urine within four Amos. Surely he was Yotzei, for it was l'Chatchilah to bless as long as he does not know that there is urine, since even in front of urine is forbidden only mid'Rabanan. Chachamim did not decree about a Safek (76:7). Had he blessed knowing that there was urine there, the Mechaber would not say that it is obvious, for this is like one who found excrement.