ANALGESICS

By: Sathish Rajamani

INTRODUCTION

Analgesics are medications used to relieve pain without reducing the consciousness of the patient.They work by reducing the amount of pain felt and this is generally achieved by interfering with the way the pain message is transmitted by the nerves. Analgesics will not treat the cause of the pain but they will provide temporary relief from pain symptoms.

TYPES OF ANALGESICS

• OPIOID

ANALGESICS

• NON - OPIOID

ANALAGESCIS

• ADJUVANT

ANALGESICS

OPIOID ANALGESICS

The opioid analgesics which are prescription only medicines that are very potent, being chemically related to morphine.Opioid analgesics are prescribed for moderate to severe pain, particularly of visceral origin, and are used in step two and step three of the analgesic ladder.

Dependence and tolerance are well known features with regular use although this should not inhibit prescribing in palliative care.Some chronic non-malignant conditions benefit from analgesic control with opioids, but patients should be reviewed regularly. 

OPIUM, the greek name for poppy juice. Is obtained from the juice of the papaver somniferum.

ACTIONS OF OPIOID ANALGESICS

Opioid analgesics interacts with four major receptors in the CNS

Mu receptorsKappa receptorsSigma receptors and Delta receptors

RECEPTORS EFFECTS

MU Analgesia, Respiratory depression and euphoria

KAPPA Respiratory depression, sedation

SEGMA Hallucination, Dysphoria, Seizures

DELTA Analgesia

CLASSIFICATION OF OPIOID ANALGESICS

Natural AlkaloidsMorphineCodeineSemi Synthetic CompoundsPethidineMethadoneTramadol

MORPHINE

Morphine is the most important alkaloid of of opium.Morphine produces analgesia through actions in the brain and spinal cord.Morphine is readily absorbed from the GI tract and subcutaneous and muscle tissue.Morphine is administered intravenously, epidurally, and intrathecally.

PHARMACOTHERAPEUTICS

Morphine sulfate is primarily used to relieve moderate to severe pain.It is used pre operatively, its effect is on reducing patients anxiety and in assisting in induction of anesthesia.It is the drug of choice for clients with pain from MI, Pulmonary edema and dyspnea from acute left ventricular failure.

PHARMACOKINETICS

Absorption• It depends on the route of

administration,• Morphine ingested orally is

generally absorbed in one and half to two hours.

• It reaches liver for metabolism before reaching systemic circulation.

• Absorption after IM or SC injection occurs in 30 to 60 minutes.

PHARMACOKINETICS

Distribution• It occurs quickly.,• After administration morphine

leaves the blood and directly enters the kidney, lungs, liver and spleen.

• Its action on skeletal muscle is limited, since the drug is not very lipid soluble, it does not cross the BBB easily

• .

DURATION OF ACTIONMETHOD OF ADMINISTRATION ONSET OF ACTION

Oral 4 to 12 hours

IM or SC 10 to 30 minutes

IV 15 to 30 minutes

PHARMACOKINETICS

BIOTRANSFORMATION

• It occurs in the liver.• Excretion occurs in the kidney.

• Only traces of morphine is founded in body after 48 hours..

PHARMACODYNAMICS

Morphine produces analgesia by binding preferentially to the mu and delta receptors.Morphine targets the areas involved with regulation of pain perception, respiration and affective behaviors.

THERAPEUTIC USES

AnalgesiaSuppression of cough and dyspnea.SedationIn the treatment of diarrheaAs preanesthetic medicationIn the treatment of the left ventricular failure.

CONTRAINDICATIONS

Head Injury, because morphine can cause increased intracranial tension, which can leads to marked respirator depression.MyxedemaBronchial asthma – Morphine releases histamine which can trigger bronchoconstriction.Elderly patientsIn hypotensive states.

ADVERSE REACTIONS

CNS Side effects

Confusion, anxiety, lethargy, nausea and vomiting.GIT Side effects

ConstipationOther Side effects

Urinary retention, dry mouth, dysphoria, hypotension, skin rash, itching and urticaria.

MORPHINE POISONING

Acute poisoning with morphine and other opioids occurs with overdoses.Signs and SymptomsComa, Pinpoint pupils, and respiratory depression which frequently called triad.

TREATMENTAdministration of antagonist

Naloxone.Support of Respiratory and Cardio

Vascular function.