Observation medicine in New Zealand has grown considerably in the last decade, driven by the shorter stays in emergency departments health target and the growth of emergency medicine as a specialty. Evidence that the growth of this service has mostly been appropriate and within suggested guidelines, is indicted by most hospitals admitting < 20% of patients to their emergency medicine governed observation unit and most subsequently admitting < 20% of these to an in-patient ward. Average lengths of stay are less than 12 hours and caseloads commonly include toxicology, low-risk chest pain and abdominal pain although the gamut of minor medical and surgical conditions are seen.

Zonisamide (1-(1,2-Benzoxazol-3-yl)methanesulphonamide) is a sulphonamide derivative with a molecular weight of 212.2 and a molecular formula of C8H8N2O3S.

Fludrocortisone acetate (9α-fluoro-11β,17α,21-trihydroxypregn-4-ene-3,10-dione 21-acetate) is a synthetic adrenal steroid. It has a molecular weight of 422.5 and a molecular formula of C23H31FO6.

Amitriptyline hydrochloride (3-(10,11-dihydro-5H-dibenzo[a,d]cycloheptene-5-ylidene)-N,N-dimethylpropan-1-amine; hydrochloride) has a molecular weight of 313.9 and a molecular formula of C20H23N,HCl. Amitriptyline is usually given as the hydrochloride and doses are expressed in terms of this salt. Amitriptyline hydrochloride 75 mg is equivalent to about 66.3 mg of the base.

Oxybutynin (4-diethylaminobut-2-ynyl 2-cyclohexyl-2-phenylglycolate; 4-(diethylamino)-2-butynyl α-phenylcyclohexaneglycolic acid ester) has a molecular weight of 357.5 and a molecular formula of C22H31NO3.

Nortriptyline hydrochloride (3-(10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5-ylidene)propyl(methyl)amine hydrochloride) is a dibenzocycloheptadiene tricyclic antidepressant with a molecular weight of 299.8 and an empirical formula of C19H21N,HCl.

Droxidopa ( (–)-threo-3-(3,4-dihydroxyphenyl)-l-serine) is an odourless, tasteless, white to off-white crystalline powder, which is slightly soluble to water. It has a molecular weight of 213.2 and a molecular formula of C9H11NO5.

Citalopram (1-[3-(dimethylamino)propyl]-1-(4-fluorophenyl)-3H-2-benzofuran-5-carbonitrile) is a fine white to off-white powder with a molecular weight of 324.4 and an empirical formula of C20H21FN2O. Citalopram 20 mg is equivalent to 24.99 mg citalopram hydrobromide.

Amantadine (tricyclo[3.3.1.1]decan-1-amine, 1-adamantanamine, 1-aminoadamantane) is a white or nearly white crystalline, odourless, and bitter-tasting powder, with a molecular weight of 151.25 and an empirical formula of C10H17N. Amantadine is a tricyclic amine with two available preparations, amantadine hydrochloride, which is given orally, and the salt amantadine sulphate, which is administered either orally or IV.

Melatonin (N-acetyl-5-methoxytryptamine or N-[2-(5-methoxy-1H-indol-3-yl)ethyl]acetamide) is a tryptophan-derived hormone and an antioxidant, produced primarily in the pineal gland. Exogenous melatonin is an amphiphilic, white–cream to yellowish crystalline powder, unchanged in the entire pH range. It has a molecular weight of 232.28 and an empirical formula of C13H16N2O2, while its chemical structure resembles serotonin.

Istradefylline (8-[(1E)-2-(3,4-dimethoxyphenyl)ethenyl]-1,3-dethyl-7-methyl-3,7-dihydro-1H-purine-2,6-dione) is a xanthine derivative with a molecular weight of 384.4 and an empirical formula of C20H24N4O4.

Apomorphine hydrochloride (6aβ-aporphine-10,11-diol hydrochloride hemihydrate; (R)-10,11-dihydroxy-6a-aporphine hydrochloride hemihydrate; (6aR)-5,6,6a,7-tetrahydro-6-methyl-4H-dibenzo[de,g]quinoline-10,11-diol hydrochloride hemihydrate) has a molecular weight of 303.8 and a molecular formula of C17H18ClNO2.

Midodrine hydrochloride (2-amino-N-(β-hydroxy-2,5-dimethoxyphenethyl)acetamide hydrochloride or (RS)-N-(β-hydroxy-2,5-dimethoxyphenethyl)glycinamide hydrochloride), molecular weight 290.74 and a molecular formula of C12H18N2O4,HCl.

Rivastigmine ([3-[(1S)-1-(dimethylamino)ethyl]phenyl]N-ethyl-N-methylcarbamate) can be found as an off-white to slightly yellow powder in oral formulations or a viscous, clear, and colourless to yellow to very slightly brown liquid in transdermal formulations. It has a molecular weight of 250.34 (as the base) and an empirical formula of C14H22N2O2.