Have had lower back pain for 2 weeks since taking doxcycline (100mg per day as anti malarial). Most likely cause would be awkward/long flight or a strain lifting/moving luggage but of course, i started taking it about a day before leaving, shortly before I started lifting heavy bags to check their weight etc! Just wanted to know if there could be a connection to the medicine and if so serious implications/anything to watch out for? Many thanks!