Lisdexamfetamine (Elvanse) is a pharmacologically inactive prodrug. Following oral administration, lisdexamfetamine is rapidly absorbed from the gastrointestinal tract and hydrolysed primarily by red blood cells to dexamfetamine, the active drug. 

Onset of action is one to two hours and duration of action is up to 13 hours. The capsule may be swallowed whole. For patients with swallowing difficulties (e.g. younger children), it can be opened and the contents emptied and mixed with a soft food such as yoghurt. Alternatively, it can be mixed with a glass of water or orange juice, stirred and taken immediately.

Atomoxetine (Strattera) provides up to 24 hours’ cover and has less potential for drug abuse. However, a major drawback is that it takes about four weeks to start working and may take up to three months to take full effect. During the start of atomoxetine treatment, the clinician may decide to overlap with methylphenidate and then slowly withdraw the latter. 

The safety of atomoxetine has been studied to 1.8mg/kg/day but evidence for efficacy above 1.2mg/kg/day is lacking. Atomoxetine should be given once daily in the morning. If tolerability or response is not satisfactory, the dose can be split to be given in the morning and late afternoon or early evening.  

Guanfacine (Intuniv) provides up to 24 hours’ cover. Its onset of action is quicker than atomoxetine (around three weeks) but weekly dose titration of 1mg to an optimal dose takes time and requires weekly blood pressure and pulse checks with each change. 

Any dose reductions need to be gradual. Dosing is based on the patient’s weight with the maintenance dose ranging between 0.05-0.12mg/kg/day rounded up to the nearest dosage form available.

Melatonin is a hormone thought to regulate the wake-sleep cycle. Melatonin may be prescribed in patients with ADHD if their insomnia is causing daytime impairment. Typically, doses of between 1-10mg at night are utilised to help initiate or maintain sleep. Rarely, higher doses of up to 14mg have been used. 

The range of melatonin preparations licensed in under-18s and specifically for ADHD is growing. Adaflex tablets is a recent example and a licensed liquid preparation is going to enter the market soon. 

Each area prescribing committee will ultimately make its own decision about whether to approve these medications, but it would be difficult to ignore the licensing status. Community pharmacy may gradually see reduced use of off-label Circadin or other unlicensed formulations, although stable patients may still remain on them depending on whether prescribing committees advocate active switches for existing patients. 

It is worth noting that Adaflex is an immediate release formulation whereas Circadin is slow release. Melatonin oral solution and suspension in varying strengths still features in part VIIIB of the Drug Tariff.