Diazepam
The most familiar of the benzodiazepines is diazepam, usually administered at a
dosage of 250 ug/kg. For a 6-year-old child this is approximately 5 mg but could be as
low as 3.9 mg or as high as 6.6 mg. For a much older patient, for example, a 15-year
old, the average dose would be 13.6 mg and may vary from 9.7 mg to 18.9 mg.
Midazolam
Midazolam is another benzodiazepine that is more commonly used as an intravenous
agent. However, its use as an oral sedative is growing though, currently it does not
have a product licence for this application. The intravenous liquid is bitter to taste and
so the preparation is often mixed with a fruit flavoured drink. The oral dose is higher
(0.3-0.7 mg/kg) than the intravenous dose because the oral midazolam reaches the
systemic circulation via the portal circulation which decreases the drug's
bioavailability, necessitating a higher oral dosage. Evidence is still relatively scant,
especially in children under 8 years of age, and so the use of oral midazolam is still
largely restricted to specialist hospital practice.
Chloral hydrate
Chloral hydrate is a chlorinated derivative of ethyl alcohol, the 'Micky Finn'. It is a
weak analgesic and psychosedative with an elimination half-life of about 8 h. In small
doses (40-60 mg/kg, but not exceeding 1 g), mild sedation occurs but it can be
ineffective in the management of the more anxious child. Nausea and vomiting are
common due to gastric irritation. The drug also depresses the blood pressure and the
respiratory rate, myocardial depression and arrhythmia can also occur. Recently, there
has been concern that there is a risk of carcinogenesis. Although it is still in
widespread use around the world it is gradually becoming obsolete.
Other drugs
There are other oral sedative drugs that are commonly reported in the literature in
relation to paediatric dental sedation. These include: hydroxyzine hydrochloride and
promethazine hydrochloride (psychosedatives with an antihistaminic, antiemetic, and
antispasmodic effect), and ketamine which is a powerful general anaesthetic agent
which, in small dosages, can produce a state of dissociation while maintaining the
protective reflexes. Common side-effects of hydroxyzine hydrochloride and
promethazine hydrochloride are dry mouth, fever, and skin rash. Side-effects of
ketamine include hypertension, vivid hallucinations, physical movement, increased
salivation, and risk of laryngospasm, advanced airway proficiency training is,
therefore, essential. Ketamine carries the additional risk of increase in blood pressure,
heart rate, and a fall in oxygen saturation when used in combination with other
sedatives.
Evidence to support the single use of either hydroxyzine hydrochloride, promethazine
hydrochloride, or ketamine is poor.
Monitoring during oral sedation