Disadvantage of minocycline in triple antibiotic paste used for disinfection of root canal prior to revascularization is:
Triple antibiotic paste
Consists of metronidazole, ciproﬂoxacin, and minocycline in a macrogol propylene glycol ointment.  It is inserted into the canal with a sterile lentulospiral and left in the canal for 2-4 weeks.
Advantages:

Very eﬀective in elimination of intracanal microbes.
Broad spectrum action.
Easy to prepare as ingredients are easily prepared.

Disadvantages of Triple Antibiotic Paste:

Diﬃcult to test the antimicrobial eﬀectiveness in endodontic models due to absence of an inactivator to prevent the carryover eﬀect.
Combination of bactericidal and bacteriostatic antibiotic is not rational scientiﬁcally.
Tetracycline analogs like minocycline can cause discoloration of tooth due to diﬀusion into dentinal tubules. Hence the mix should never be left in the coronal pulp chamber.
Mutation of certain microbes
Development of resistance
Increase in brittleness of tooth
Crown discoloration