Dexamethasone

Dexamethasone (中文: 地塞米松)is a reversible acetylcholinesterase inhibitor. Rivastigmine is selective for the CNS and is used for the treatment of mild to moderate dementia associated with Parkinson’s disease.

Indications include:

• Inflammatory bowel disease
• Asthma
• Croup in children
• dermatitis
• Rheumatoid arthritis
• Cerebral oedema associated with malignancy
• Counteract nausea and vomiting effects of cancer chemotherapy
• Administered before antibiotics in cases of baceterial meningitis. It reduces the inflammatory response, thus reducing hearing loss and neurological damage.
• High-attitude cerebral edema (HACE) and high-attitude pulmonary edema (HAPE), help climbers to cope with complications of high-attitude sickness

Equivalent anti-inflammatory doses of steroids

Prednisolone 5 mg is equivalent to	Betamethasone 750 micrograms
	dexamethasone 750 micrograms
	hydrocortisone 20 mg
	methylprednisolone 4 mg
	triamcinolone 4 mg

Pronunciation

Dexamethasone 0.5mg

Drug Names

Generic Name	HA Code 藥物代碼	Classification藥物分類
Dexamethasone Tablet 0.5 mg	DEXA01	P1S1S3
Dexamethasone Tablet 4 mg	DEXA19	P1S1S3
Dexamethasone 0.1% + Chloramphenicol 0.5% Eye Drops 5ml	DEXA16	P1S1S3
Dexamethasone 0.1% + Neomycin 0.5% Eye Drops 10ml	DEXA04	P1S1S3

Mechanism of Action

Immunosuppression agent,

Steroid replacement agent,

Anti-inflammatory agent

Dosage

Dosages of steroids vary widely in different diseases and in different patients.

When long-term steroid therapy is used in some chronic diseases, the adverse effects of treatment may be great. To minimize side-effects the maintenance dose should be kept as low as possible.

Steroids are used both topically (by rectum or eye) and systemically (by mouth or intravenously).

Whenever possible local treatment with creams, intra-articular injections, inhalations, eye-drops or enemas should be used in preference to systemic treatment.

The suppressive action of a steroid on cortisol secretion is least when it is given as a single dose in the morning.

Oral	usual range 0.5 – 5 mg daily
Child dose	每日10-100mg/kg

Cerebral oedema

by intravenous injection	8-16 mg initially, then 5 mg by intramuscular or intravenous injection every 6 hours until the symptoms of edema subside for 2-4 days, then gradually reduced and stopped over 5-7 days.
By intra-articular injection	0.8 – 4mg of dexamethasone (as sodium phosphate) are used depending upon the size of the joint.
For soft-tissue injection	2 – 6 mg are used.

For topical application in various skin disorders, concentrations of dexamethasone in the range of 0.02 to 0.1% is used in creams, ointments and lotions. Whereas for eye or ear preparations, concentrations are commonly 0.05 to 0.1%.

Side Effects

Short-term use

include nausea and feeling tired. More severe side effects include psychiatric problems including euphoria, nightmares, insomnia, irritability, confusion, suicidal thoughts and behavioral disturbances. This may occur in about 5% of people.

Long-term steroid use

Adrenal suppression
Steroid-induced diabetes
Osteoporosis, muscle wasting and weakness	which is a danger, particularly in the elderly, as it can result in osteoporotic fractures for example of the hip or vertebrae
Susceptibility to infection
Cushing’s syndrome	moon face, striae, and acne
Endocrine side effects	menstrual irregularities and amenorrhea, hirsutism, weight gain, hyperlipidemia
Neuropsychiatric side effects	aggravation of schizophrenia, aggravation of epilepsy, insomnia, irritability, mood changes
Dermatological effects	easy bruising, impaired wound healing, and thinning of skin
Ophthalmic effects	glaucoma, corneal or scleral thinning and exacerbation of ophthalmic viral or fungal disease

Side-effects can be minimized by using lowest effective dose for minimum period possible.

Pharmacokinetics

Dexamethasone is readily absorbed from the gastrointestinal tract.

Plasma half-life is about 190 minutes.

Binding of dexamethasone to plasma proteins is about 77%.

Up to 65% of a dose is excreted in urine within 24 hours.

Drug Management

Monitoring

• Elderly (close supervision required particularly on long-term treatment)
• Frequent monitoring required if history of tuberculosis (or X-ray changes)
• blood sugar level, blood pressure, mood change,
• monitoring of the fluid intake and output, and daily weight records may give early warning of fluid retention.
• Sodium intake may need to be reduced and calcium and potassium supplements may be necessary.
• Back pain may signify osteoporosis
• Height should be monitored in children receiving prolonged therapy with inhaled or nasal steroid.

Drug interaction

Interactions do not generally apply to steroid used for topical action including inhalation, unless specified.

Drugs given with steroid	Potential adverse drug interactions
NSAIDs	Increased risk of gastro-intestinal bleeding
Rifampicin	Accelerate metabolism of steroid so reduce the effects of steroid
Antidiabetics	Steroid antagonize hypoglycaemic effect. Requirements of antidiabetics may be increased.
Antiepileptics: Carbamazepine Phenobarbitone phenytoin	Accelerate metabolism of steroid so reduce the effects of steroidd
Antifungals: amphotericin	Increased risk of hypokalaemia
Antivirals: ritonavir	Increase plasma concentration of steroid – increased risk of adrenal suppression
Digoxin	Increased risk of hypokalaemia
Diuretics: frusemide hydrochlorothiazide	antagonize diuretic effect, increased risk of hypokalaemia
Oral contraceptive (oestrogens)	Increase plasma concentration of steroid
Theophylline	Increased risk of hypokalaemia

Caution

• Children and adolescents (growth restriction possibly irreversible)
• Osteoporosis (post-menopausal women at special risk)
• Recent myocardial infarction, congestive heart failure
• Glaucoma (including family history)
• Ocular herpes simplex – risk of corneal perforation
• Psychiatric disorders (particularly if history of steroid-induced psychosis)
• Epilepsy
• Peptic ulcer
• Hypothyroidism
• Ulcerative colitis
• Diverticulitis
• Thromboembolic disorders
• Myasthenia gravis

Contraindication

• acute infections
• patients with active or doubtfully quiescent tuberculosis
• concurrent treatment live virus vaccines for at least 3 months afterwards

Hepatic impairment

When steroids are administered orally or parenterally, the plasma-drug concentration may be increased in patients with hepatic impairment. The patient should be monitored closely.

Renal impairment

Should be used with caution in patients with renal impairment.

Pregnancy

Dexamethasone should only be used in pregnant women when benefits outweigh the risks.

• No convincing evidence that systemic steroids increase the incidence of congenital abnormalities such as cleft palate or lip.
• Prolonged use increases the risk of intra-uterine growth; but no evidence of intra-uterine growth restriction following short-term treatment.

Note

Prolonged use of steroid	Advice to patient
Immunosuppression Prolonged use can increase susceptibility to infection	Avoid contact with people who have chickenpox, shingles, or measles.
Adrenal suppression Steroid suppresses the endogenous secretion of corticotropin by the anterior pituitary, resulting the adrenal cortex becomes atrophied. If given for more than 3 weeks, treatment must not be stopped gradually.	Patient must mention the course of steroid when receiving treatment for intercurrent illnesses or trauma such as surgery.

FAQ

How should I take the tablet?

Follow all directions on your prescription label. Use prednisolone exactly as directed on the label. Steroids are associated with a risk of GI irritation. The tablet MUST be with or after food to help reduce side-effects.

What should I avoid while taking?

Avoid abruptly discontinue the medication. Should not be taken with NSAIDs.

What happen if I overdose?

Contact your primary care doctor. If emergency situation, call 999

What happen if I miss a dose?

Take it as soon as you remember. If it is near the time of the next dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up.