i. Dextromethorphan HBr ii. Levo proproxyphene napsylate (Novrad) iii. Codeine phosphate (Zenodyl) iv. Pholcodine (Ethnine, Simplex) - Synthesis and Drug Profile
Synthesis
Properties and uses: Dextromethorphan hydrobromide (HBr) is a white
crystalline powder, sparingly soluble in water, and soluble in alcohol. It is a
substituted dextro isomer of the opioid levomethorphan.
It is not an
analgesic or an addictive. Dextromethorphan HBr should not be given to patients
who are on monoamine oxidase inhibitors therapy. It is an opioid receptor
agonist used as a cough suppressant.
Assay: Dissolve the sample in a mixture of 0.01 M hydrochloric acid and
alcohol (1:4) and titrate against 0.1 M sodium hydroxide. Determine the end point
potentiometrically. Read the volume added between the two points of inflexion.
Properties and uses: It is a white, bitter, crystalline powder,
odourless, soluble in water, alcohol, or chloroform. It has little or no
analgesic activity. It has been found to be relatively less potent than codeine
in the treatment of cough reflexes. The (–)-isomer of the drug showed greater
antitussive activity in comparison to either the (+)-isomer or the racemic
mixture.
Dose: Usually 50–100 mg after every 4 h.
Synthesis
Synthesis
Properties and uses: Codeine phosphate is a white crystalline powder,
soluble in water, and slightly soluble in ethanol. This drug acts by
suppression of the cough centre in the brain stem.
Assay: Dissolve the sample in a mixture of anhydrous acetic acid and
dioxan (1:2) and titrate against 0.1 M perchloric acid using crystal violet as
indicator.
Dose: 10–20 mg every 4 to 6 h.
Dosage forms: Co-codamol tablets B.P., Effervescent co-codamol tablets B.P.,
Co-codaprin tablets B.P., Dispersible co-codaprin tablets B.P., Codeine linctus,
paediatric Codeine linctus B.P., Codeine phosphate injection B.P., Codeine
phosphate oral solution B.P., Codeine phosphate tablets B.P.
Synthesis
Properties and uses: Pholcodine is a white crystalline powder,
sparingly soluble in water, soluble in acetone, alcohol, and dilute mineral
acid. It is as effective as codeine. It is a cough suppressant with mild
sedative, but practically negligible analgesic action. It is employed for the
relief of unproductive cough.
Assay: Dissolve the sample in anhydrous acetic acid, warm gently and
titrate against 0.1 M perchloric acid. Determine the end point
potentiometrically at the second point of inflexion.
Dose: The dose for adults is 5–15 mg, for children over 2 years 5 mg,
for children below 2 years 2.5 mg.
Dosage forms: Pholcodine linctus B.P., Strong pholcodine linctus B.P.
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