Most prime macro lenses are suitable for distant subjects. However, there are some exceptions:

• the king of macro photography, Canon MP-E 65, will not focus far enough to fit more than an eye or nose on a portrait;

• some macro lenses, like Pentax DA 35 Limited Macro, have a short focal length -suitable for distant subjects only as environmental shots showing context rather than details of the subject; shorter than about 50mm on APS-C or 75mm on full frame are generally not considered suitable as portrait lens;

• some zoom lenses are also sold as "macro" lenses; generally they have a variable aperture similar to consumer zooms. You can take portraits with them, but you have to use other tricks to get a good background separation (e.g. background far away, plain background, lighting subject to underexpose background).

Macro lenses are made to be comfortable for precise manual focusing (because that's how macro is mostly done), so their large focusing range is spread over almost a full turn of focusing ring. This implies that auto-focus can be a bit slow, especially if there's no focus range limit switch and the lens goes hunting through the whole range. Prefocusing to an approximate distance might help you here in many cases.

Another disadvantage in using macro lenses compared to a regular primes lens is their moderate maximum aperture for a prime of similar focal length (especially ones preferred for low-light, fast action or portraiture), usually in range of f/2.8 to f/4.5 - for macro, more would be overkill. Tamron 60mm f/2.0 is a surprising exception here; unfortunately 60mm has to be so close to subject it will scare away living critters, also lighting becomes challenging; so it has somewhat limited use in macro world.

The smaller aperture means less flexibility in getting thin depth of field. But small maximum aperture means the aperture for maximum sharpness is even slower (typically by a stop or two), meaning you have to take harder compromises between sharpness and background separation by DOF.

That said, an f/2.8 macro lens is still on par with professional zooms aperture-wise.