Brief Answer:
Prescribed antibiotic, metronidazole and probiotic

Detailed Answer:
Hi.
Thanks for your query and an elucidate history.

To recapitulate: M / 62 - sore anus couple of days - mucus and blood in stool - bright red blood on toilet paper - normal colonoscopy 6 months ago - leaving for 7 - day cruise - wants to know further.

As pr the history you have provided this appears to be enterocolitis, infection of the intestines giving you symptoms you have posted.
This can be very well treated ASAP so that you can have the best trip on the cruise.
The treatment can be in the form of an antibiotic active against intestinal pathogens, metronidazole and probiotics.

So to answer your query: you should not wait till you come back- start the treatment immediately to get an early results, enjoy the trip and you will be alright before you come back. This does not look to be something more serious that would prevent you going on the cruise.

I hope this answer helps you to get a cure; consult your Doctor to get a prescription based treatment...

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Brief Answer:
Please get a prescription of a local Doctor.

Detailed Answer:
Sir, Prescription can not be given on the web / net.
Please try to get one from the local Doctor.
Better may be Cefixime, Metronidazole and any probiotic. (These may be prescription medicines in your country), Pharmacist may be of more help to tell the reality and may help you to get a prescription.

Please keep the area cleaned with warm water and then wipe dry or dry-up with hair dryer.
Try to keep the area aerated / ventilated whenever possible.

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