Morphine sulphate injection

What is Morphine sulphate

Morphine sulphate injection is an opium alkaloid and a standard potent opioid analgesic. This opioid acts as an anxiolytic, hypnotic and sedative.

It causes both the  stimulation and the depression of the central nervous system.

The depression caused by morphine leads to analgesia, respiratory depression, depression of cough reflex and sleep and the stimulation leads to vomiting, miosis, hyperactive spinal cord reflexes and even convulsions. Morphine changes the mood and causes euphoria or even dysphoria.

morphine sulphate injectionMorphine sulphate injection Dose

The usual dose in adults ranges from 10 to 20 mg (0.1 to 0.2 mg/kg) i.m. For intravenous (i.v.) use smaller doses may be given. Following i.v. and i.m. administration analgesia reaches a peak in 20 min and 90 min respectively and the duration is more or less 4 h.

Morphine sulphate injection effects and side effects

Morphine stimulates some smooth muscles and may lead to gastrointestinal muscle spasm, biliary tract spasm and even renal tract spasm. It should be avoided in renal and biliary colic. It causes constipation.

Morphine sulphate directly depresses the medullary respiratory center. The carbon dioxide response curve is flattened and shifted to the right.

Morphine depresses respiration both in rate and depth. It reduces sensitivity of respiratory center to increase blood carbon dioxide tension. It depresses vasomotor control and hypotension may occur due to impaired vascular reflexes, reduced sympathetic activity and release of histamine.

Bradycardia may occur from stimulation of vagal center. Postural hypotension may be further exaggerated if opioids are given to patients with decreased intravascular fluid volumes. Cutaneous vasodilatation and sweating may occur.

Bronchospasm may also occur due to histamine release. This drug can cause severe feeling of  itching. Urinary retention is a common side effect.

It reduces the metabolic rate and depresses the heat regulating center. It may release histamine and 5-hydroxytryptamine. It causes addiction. It may cause some hyperglycaemic effect. It causes antidiuresis by releasing antidiuretic hormone. Morphine  sulphate passes through placental barrier and affects fetus. It tends to prolong childbirth.

Tolerance occurs to morphine sulphate. The dose may have to be increased to obtain the same degree of effect. Abstinence syndrome occurs due to sudden withdrawal of morphine in an addict.

Morphine Sulphate metabolism

Morphine is metabolized in the liver by conjugation and the conjugated metabolites are rapidly excreted by the kidneys. It may appear in breast milk, saliva and sweat. It is poorly absorbed in gastrointestinal tract and so it is better injected to get the analgesic effect.

Morphine sulphate Uses

Morphine sulphate is mainly used to relieve pain, in preanesthetic medication, to relieve anxiety and in left ventricular failure.

The analgesic action of morphine sulphate is due to elevation of the pain threshold at spinal and thalamic levels and diminution of the emotional component.

Profound and prolonged analgesia may be obtained by extradural and intrathecal administration of morphine sulphate. Spinal opioid receptors are located in substantia gelatinosa.

Morphine sulphate should be carefully used in extremes of ages, cachectic debilitated patients, in respiratory cripples, in endocrine disorders like hypothyroidism and hypopituitarism, in liver and kidney diseases, in patients with raised intracranial tension, in pregnancy, in hypersensitive cases and in patients treated with monoamine oxidase (MAO) inhibitors.

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