Article Notes
- (CH3)3-N-CH2CH2-OCO-CH2CH2-OCO-CH2CH2-N-(CH3)3
- pH 3.5
- Shelf life 3 years at 4°C, though only 'months' at 20°C.
- Dose - ED95 0.5 mg/kg, IV 1.5 mg/kg, IM 2.5-4 mg/kg.
- Absorption - IM, IV.
- Distribution - >0.2 L/kg; crosses placenta slightly but little effect on foetus.
- Protein binding ?
- Onset 30s IV, 2-3 min IM; Offset 3-5 min.
- Metabolism - PChE to succinylmonocholine (5% activity) & choline -> succinic acid & choline.
- tß½ 5 minutes
- Mechanism - binds to alpha subunit of nicotinic ACh receptor, producing persistent depolarisation (phase 1 & phase 2 blocks).
- CNS - ⇡ intra-ocular pressure (4-8 mmHg rise), ⇡ intra-celebral pressure (to 30 mmHg at 2-4 min).
- CVS - arrhythmias (both bradycardia & tachycardia possible), ⇡ systolic blood pressure, (both negative inotropic and chronotropic effects).
- Resp - 'sux apnoea' pharmacogenetic diversity (94% normal, 3.8% heterozyg (10 min duration of effect), <1% homozog (1-2h duration))
- Renal - hyperkalaemia due to K+ release from muscle; beware in neuromuscular conditions, denervation, and extensive burns.
- GIT - ⇡ intragastric pressure, ⇡ secretions, salivation.
- SEs - anaphylaxis, malignant hyperthermia, sux apnoea, muscle pains, masseter spasm.
Note this is a systemic review of a small number of RCTs published very early in the COVID-19 pandemic, and notably only one of the four RCTs included coronarvirus, Loeb (2009), the others mainly focusing on influenza [MacIntyre (2011), MacIntyre (2013), Radonovich (2019)]. Obviously none of the studies specifically looked at SARS-CoV-2.
Subsequent N95/P2 mask studies since this have shown significant benefit of high-quality masks in reducing COVID-19 transmission.
As of February 28th 2023, pholcodine has FINALLY been banned in Australia by the Therapeutic Goods Administration (TGA).
Press release here: TGA - Pholcodine
It's very sad that it took 14 years after Florvaag & Johansson's landmark 2009 paper describing the connection between pholcodine and NMBD anaphylaxis, for this problem to be addressed.
How many patients were exposed to avoidable harm?
See the more recent 2022 article, Return to exercise post-COVID-19 infection: A pragmatic approach in mid-2022, which also sets out a graduated return to exercise, though is perhaps even more pragmatic.
The usual 'correlation is not causation' qualifier is very necessary here. Perhaps doubly-so because this is a meta-analysis using pooled data of over 1 million people.
It's completely possible that someone who chooses to receive an influenza vaccine is also someone who makes more cautious health decisions and is more risk-averse, reducing their COVID exposure risk. The vaccinated are also more likely to be from better health-serviced locations and probably from higher socio-economic groups.
Still, interesting association nonetheless.
This study is primarily an evaluation of a specific RAT, the Coris coronavirus disease 2019 Ag Respi-Strip test – which while showing poor sensitivity, it again demonstrates that RAT-positivity correlates with viral load. This study used PCR-detection as the gold standard for evaluation, which because of the extreme sensitivity of PCR testing, does not easily translate to assessment of contagiousness (although Ct > 25-30 seems to correlate with inability to grow in viral culture).
Early 2021 update of the 2020 Cochrane Review: Rapid, point-of-care antigen and molecular-based tests for diagnosis of SARS-CoV-2 infection.
Better data is now available on correlation between PCR cycle threshold and likely infectivity.
Early 2020 studies of COVID rapid antigen tests were of low quality and of variable applicability to COVID diagnostic decisions. This situation improved dramatically in 2021 and 2022, and many RATs are now continually validated in existing and emerging variants.
This Cochrane Review was updated in 2021.
Suxamethonium chloride (suxamethonium, succinylcholine or sux) is a depolarising muscle relaxant that produces rapid-onset, short-duration, deep muscle relaxation. First identified in 1906 and used medically in 1951, it is one of the oldest anaesthesia drugs still widely used. Due to its unique properties and low cost, it remains on the World Health Organisation's List of Essential Medicines