Dr Sharon Rees @reesprescribe
Day 1: #melatonin is derived from the pineal gland & was first isolated in the late 1950s. Named from observation of altered frog pigmentation, but the role for human melanin is unknown. Known for circadian rhythm & sleep promotion, but has diverse effects, including immunomodulation & bone remodelling
Dr Sharon Rees @reesprescribe
Day 2: #melatonin is licensed in adults to manage short-term insomnia & jet lag. One named tablet is licensed for use in children with ASD or Smith-Magenis Syndrome. Insomnia dose range 2-10mgs at bedtime. There is high demand for #melatonin to manage sleep issues related to childhood conditions such as ADHD, as well as from medicines which cause insomnia e.g methylphenidate. Many unlicensed ‘Specials’ options are available for children, which can also be high cost
Dr Sharon Rees @reesprescribe
Day 3: High oral absorption but high 1st pass metabolism leading to 15% bioavailability. Food increases absorption. High Vd. Rapid liver metabolism via CYP1A enzymes. Renal excretion. Short t½ 0.5-1hr (i.r). Avoid m.r if hepatic impairment; avoid i.r if mod-severe. Caution for m.r/i.r if renal impairment
Dr Sharon Rees @reesprescribe
Day 4: Darkness leads to the internal production of #melatonin as derived from serotonin. This interacts with brain melatonin receptors MT1 & MT2 as part of the sleep-wake cycle control; higher levels of #melatonin promote onset & duration of sleep. There is an age-related decrease in endogenous melatonin levels, as well as decreased levels linked to lower oestrogen & some psychiatric disorders. Therefore replacement therapy can improve sleep quality. For insomnia, timing of drug important i.e 1-2 hrs before bed (slow release)
Dr Sharon Rees @reesprescribe
Day 5: ADEs: Overall #melatonin is considered a non-toxic intervention. Arthralgia & pain common. Anxiety, abnormal dreams, GI disorders, rash uncommon. Rare leucopenia, mood change, priapism. Hyperglycaemia ‘unknown frequency’; recommended not to take i.r tablet within 2 hours of meal. Monitor seizure frequency for those with epilepsy (NOT exhaustive)
Dr Sharon Rees @reesprescribe
Day 6: Drowsiness is expected with #melatonin, as is a synergistic effect with all drugs which produce sedation. Enzyme inhibitors eg fluvoxamine (only ‘severe’ DDI listed in the BNF) & quinolones can increase exposure. Oestrogens also can increase levels; caution with CP/HRT. It is noteworthy that alcohol & smoking can reduce the effects of #melatonin on sleep. NSAIDs, as well as beta blockers, if taken in the evening can suppress endogenous melatonin & lower efficacy too (NOT exhaustive)
Dr Sharon Rees @reesprescribe
Day 7: Unlike other sleep medicines, there is no known addiction or withdrawal issues from #melatonin. However, data is on short-term use & psychological dependence is possible. There is low grade evidence of delayed puberty linked to long duration of use
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In addition to the tweets, read the BNF monograph on melatonin and the treatment summary for ‘hypnotics and anxiolytics’. Another useful source is the Summary of Product Characteristics for melatonin – see links below. Once you have completed this, answer the 10 questions. Submit your answers to reesprescribe@gmail.com. If you answer at least eight out of 10 questions correctly, you will receive your CPD certificate via email.