Without a doubt, co-codamol tablets are one of the most popular over the counter products purchased from the pharmacy. Why is co-codamol so popular?
Co-codamol over the counter: legal status
Co-codamol tablets have a legal status of a pharmacy only medicines (P medicine) which means it can only be sold by or under supervision of a pharmacist. Codeine-containing products are restricted to 3-day use only (due to addictive properties), therefore it is recommended that one pack of co-codamol can be sold per patient.
Co-codamol tablets are indicated for the short-term treatment of acute moderate pain which is not relieved by paracetamol, ibuprofen or aspirin alone.
What does co-codamol over the counter contain?
Co-codamol contains two active ingredients: paracetamol and codeine.
Over the counter, co-codamol tablets contain 500mg of paracetamol and 8mg of codeine (8/500). Branded versions of products containing higher amounts of codeine combined with paracetamol are available over the counter. For example, Solpadeine Max contains 12.8mg of codeine and 500mg of paracetamol per tablet.
Co-codamol is available in tablet and effervescent formulation. Effervescent tablets dissolve rapidly when placed in the water. The effervescent formulation allows for quicker absorption, hence much faster relief of the symptoms.
Can you buy co-codamol 15/500 and 30/500?
No. Higher strength of co-codamol tablets and capsules (co-codamol 15/500 and co-codamol 30/500), are available as prescription medications and cannot be purchased over the counter. Prescription only co-codamol is one of the most commonly prescribed drugs in UK.
How does co-codamol work?
The exact mechanism of action of paracetamol is not known. Paracetamol has both analgesic (helps with pain) and antipyretic properties (reduces temperature). Paracetamol does not have anti-inflammatory properties.
Codeine is classified as a weak opioid. Its analgesic actions are thought to be 1/10 of that induced by morphine (Mattia & Coluzzi, 2015). Once in the body codeine is transformed (metabolised) into different active substances, one including morphine, which is responsible for analgesics actions.
Codeine acts on opioid receptors found in the body, including the brain and gastrointestinal system. Opioid receptors have a role in pain control and transmission. When codeine/morphine binds to target receptors it stops pain signals from the brain to the affected parts of the body.
Codeine weakly binds to opioid receptors, however, its metabolite, morphine has 200-fold better affinity for those receptors (Dean, 2016). Therefore, the analgesic effects of codeine depend on how much codeine is transformed into morphine in our body.
The degree of codeine metabolism may vary largely between individuals. This means not everyone responds to co-codamol treatment in the same way. It is known that some people are poor metabolisers of codeine, hence they experience little pain relief from codeine. It is estimated that up to 7% of the Caucasian population are poor metabolisers of codeine (eMC, 2018). On the other hand, rapid codeine metabolisers have increased risk of experiencing side effects of opioid toxicity including confusion, nausea, vomiting, shallow breathing. Prevalence for rapid metabolisers of codeine is the highest amongst African/Ethiopian population with an estimated 29% of the population affected (ibid).
Concomitant use of other drugs can affect codeine metabolism, for example, patients on fluoxetine (a popular antidepressant) can experience fewer benefits (including no benefit at all) in terms of pain management when both drugs are taken together.
Side effects of co-codamol use
Patients taking co-codamol may experience the following side effects:
• Feeling sick
On prolong use:
• Addiction, dependence, and tolerance
• Worsening of headaches
Why is co-codamol over the counter addictive?
Over the counter co-codamol should not be used for more than 3 days at any given time. UK licensing for all codeine containing products requires prominent information on the packaging stating ‘Can cause addiction. For 3 days use only.’
When taken, co-codamol can cause a feeling of relaxation, drowsiness, and sometimes euphoria. All of these are caused by the release of dopamine within the brain’s reward system. Repeated use of drugs which have the potential for addiction cause changes to dopamine system within the brain contributing to addiction, physical dependence, and tolerance (more drug needed to have the same effect).
Addiction becomes prominent with physical symptoms such as cravings for the drug. In case of codeine, some signs of addiction include anxiety, mood swings, drowsiness, nausea, constipation, dry mouth and more (Read more on symptoms of codeine addiction on TalktoFrank).
Overall over the counter co-codamol may provide better pain relief than paracetamol or ibuprofen alone. However, patients need to be aware of side effects associated with codeine use and its addictive properties.
Sadly co-codamol became popular for all the wrong reason. Co-codamol is too cheap and easily accessible despite of its classification as pharmacy only medicine. Pharmacy teams need to be more vigilant and recognise repeated request for co-codamol by the same patients and refuse the sale when necessary.
Dean Laura (2016). Codeine Therapy and CYP2D6 Genotype. Available at: https://www.ncbi.nlm.nih.gov/books/NBK100662/ Accessed on 02/05/2019
Mattia C, Coluzzi F (2015). A look inside the association codeine-paracetamol: clinical pharmacology supports analgesic efficacy. Available at: https://www.ncbi.nlm.nih.gov/pubmed/25720726 Accesses on 02/05/2019
eMC (2018). Co-codamol tables 8/500 . Available at: https://www.medicines.org.uk/emc/product/5755/ 02/05/2019