BNF DRUGS.

THEOPHYLLINE. Used in asthma and copd. Metabolised in d liver. Plasma conc increased in heart failure, cirrhosis, viral infections, elderly and

by its metabolism inhibitors. Plasma conc is decreased in smokers, chronic alcoholism and drugs that

induce liver metabolism. NTR, particular care required when introducing or withdrawing drugs that

interact with theophylline. Therapeutic range 10-20mg/l, frequency and severity of adverse effects

increase above this. Given by injection as aminophylline. Must be VERY SLOW, at least over 20

minutes. Serious side effects such as convulsions and arrthymias can occasionally

precede other symptoms of toxicity.

GENTAMICIN An aminoglycoside used for bactericidal and active against gram +ive and -ive

organisms. It is broad spectrum but is inactive against anaerobes and has poor activity against haemolytic streptococci and pneumococci.

Not absorbed from d gut and must be given by injection for systemic infections.

Excretion principally by kidney and accumulation occurs in renal impairment. Treatment whenever possible shd not exceed 7 days. Important side effects

include ototoxicity and nephrotoxicity. In renal impairment, dose interval must be increased. If severe, dosed shd be

reduced as well. Once daily administration is more convenient. In patients with normal renal function, conc shd be measured after 3 or 4

doses of a multiple dose regiment. For multiple dose regimens, blood samples should be taken approx 1hr after

im or iv administration (peak) and also just before d nxt dose.

DIGOXIN. A cardiac glycoside that increases d force of contraction and reduces

conductivity alongvd AV node. Indicated for heart failure and atrial fribillation. Long halflife and maintenance doses given once daily. Renally excreted, likelihood of toxicity increases 1.5-3mcg/l. Hypokalaemia predisposes to toxicity. Managed by pottasium sparing diuretic

or pottasuim supplementation.

WARFARIN. Oral anticoagulant. Antagonises d effects of vit K and take at least 48 to 72hrs

for effect to develop fully. Main indication is deep vein thrombosis. For patients who require rapid anticoagulation, d usual adult induction dose is

10mg on d first day. Subsequent doses depend on INR. For patients who dont require rapid anticoagulation, a lower loading dose can be used over 3-4 wks. Daily maintenance usually 3-9mg taken at same time each day.

AMIODARONE. Treatment of arrythmias when other drugs ineffective. Very long half life extending to several weeks, given once daily Development of corneal microdeposits reversible on withdrawal. Patients may

be dazzled by headlights at night.

Patiends shd be advised to shield skin from light during treatment and for several months after discontinuation due to possibility of phototoxic reactions. Wide spectrum sunscreen shd be used.

Contains iodine and cn cause disorders of thyroid function. Lab tests shd be performed b4 treatment and every 6 months. Also associated with hepatoxicity and treatment should be discontinued if severe liver function abnormalities develop.