Can minocycline reverse morphine-induced respiratory depression in obstructive sleep apnea patients?- A pilot study

INTERVENTION: This is a double‐blind, placebo‐controlled, cross‐over study. All subjects will undergo 2 overnight sleep studies separated by an interval of at least 1 week. The Sleep Study measures the effects of the drug on breathing and oxygen levels during sleep. After signed and informed consent is given, participants would be prescribed a 3 day course of either active or placebo oral minocycline, depending on their randomisation. Patients will be asked to take a single loading dose of 200 mg of minocycline/placebo at around 8pm two days before the first sleep study. For the next two days patients take 100 mg minocyclin/placebo twice a day (8am and 8pm approximately), including the sleep testing day. First PSG study: Patient finishes dinner at 5pm, and takes a single dose of 30mg MS Contin (oral slow release morphine)at 5:30pm. At 8pm, the patient takes scheduled 100mg minocycline/placebo. At 9pm, patient will be tested for pain threshold (Von Frey hair test), and a short 10 minute clinical test of breathing, the central ventilatory chemosensitivity test. An indwelling venous catheter will be inserted and 5ml of venous blood will be taken for drug concentration/metabolites analysis. At 10pm, PSG sleep study starts. After awakening the next morning the patient will be discharged with the 3 days dose of cross‐over minocycline/placebo to be taken at home before the next scheduled sleep study. The second arm of the study, the procedure is identical to the first arm except the patient has been provided the opposite treatment according to the randomization schedule. Second PSG study: The procedure is identical to the first PSG night, except that the subject takes 100mg cross‐over minocycline/placebo at 8pm (the second dose of the day). CONDITION: obstructive sleep apnea PRIMARY OUTCOME: %Total sleep time SpO2 <90% during sleep. The parameter is part of the PSG measurement. Central chemosensitivity tested by ventilatory chemoreflex tesing system SpO2 (Oxygen Saturation) nadir during sleep SECONDARY OUTCOME: CO2 recruitment threshold tested by chemoreflex testing system Oxygen desaturation index (ODI) as part of PSG assessment Pain threshold (Mechanical Detection Threshold) tested by Von Frey Hair INCLUSION CRITERIA: Aged between 18‐60 years who have previously been tested by a polysomnography (PSG) study that shows they have sleep apnoea, with Apnea Hypopnea Index >15/hr and SpO2 nadir 90‐70%.