Merrimack Valley Medical Associates Pc. 421 Merrimack St Ste 201 . Methuen, MA, 01844. LOCATIONS. Merrimack Valley Medical Associates Pc. 421 Merrimack St Ste 201. Methuen, MA, 01844. Tel: (978) 725-4822. Mon 8:00 am - 5:00 pm. ... WebMD does not provide medical advice, diagnosis or treatment..