Anti-tussives
Mechanism of action:
Dihydrocodeine is involved in the suppression of the medullary cough centre.
The mechanism of action involves the metabolism of dihydrocodeine to
dihydromorphine, a high affinity mu-opioid receptor ligand in membrane
homogenates, catalyzed by CYP2D6 (Schmidt et al, 2003). The clinical study
revealed no significant difference in plasma or urine pharmacokinetics
between extensive metabolisers and poor metabolisers of CYP2D6 for
dihydrocodeine and its glucuronide. Hence, CYP2D6 phenotype has no major
impact on opioid receptor-mediated effects of a single 60 mg dihydrocodeine
dose, despite the essential role of CYP2D6 in formation of highly active
metabolites.
Contra-indications:
Respiratory failure (AMH, 2004)
Asthma
COPD
Not to be used in children <2yrs (Taylor et al, 1993)
Caution is advised in hepatic (liver) and renal (kidney) impairment
and in alcohol dependence. Codeine: avoid in acute respiratory
depression, acute alcoholism and where there is a risk of paralytic
ileus (lack of bowel movement)
(http://www.medicdirect.co.uk/med_cabinet/medicine)
Also it is advisable to avoid cough suppressants in patients with a
productive cough (NPS Pharmacy Letter, 2002)
Disease state information:
Literature suggests that dihydrocodeine should be used in the treatment of
an acute cough associated with common cold or acute upper respiratory tract
infection (URTI) and chronic cough, however, there is little evidence to
support this claim.
Protocols for the use of Dextromethorphan:
An over-the counter (OTC) cough suppressant preparation currently on the
market contains dihydrocodeine - Rikodeine linctus (eAPP Guide, 2003). From
the literature researched, however, there is little evidence-based material,
let alone recent evidence-based material, available to support the use of
dihydrocodeine in the treatment of cough.
Although Schroeder and Fahey (2004) concluded that there was no good
evidence for or against the effectiveness of OTC medications in the
treatment of an acute cough. This was possibly due to the limited number of
patients involved in each trail.
Luporini et al (1998) suggested dihydrocodeine produced a significant
decrease in cough severity. Concurrently with the relief of cough, the
number of night awakenings was decreased significantly. The limitation of
this study is that it not most recent and it was based on the efficacy and
safety of levodropropizine and dihydrocodeine on nonproductive cough in
primary and metastatic lung cancer. Although some consideration can be
taken since non productive cough is indicated.
Side Effects:
Rare but rashes, blood disorders and acute pancreatitis (inflammation of
the pancreas) have been reported after prolonged use - these may be more
pronounced as 30mg of dihydrocodeine is a full opioid dose
(http://www.medicdirect.co.uk/med_cabinet/medicine)
Drug Interactions:
None noteworthy. Avoid other medications which cause drowsiness (such as
sedating antihistamines) which may worsen the drowsiness caused by codeine
(http://www.medicdirect.co.uk/med_cabinet/medicine)
